Changes in environmental conditions affect the life activity of microorganisms. Physical, chemical, and biological environmental factors can accelerate or suppress the development of microbes, can change their properties or even cause death.
The environmental factors that have the most noticeable effect on include humidity, temperature, acidity and chemical composition environment, the action of light and other physical factors.
Humidity
Microorganisms can live and develop only in an environment with a certain moisture content. Water is necessary for all metabolic processes of microorganisms, for normal osmotic pressure in the microbial cell, to maintain its viability. Different microorganisms have different needs for water. Bacteria are mainly moisture-loving; when the environmental humidity is below 20%, their growth stops. For molds, the lower limit of environmental humidity is 15%, and with significant air humidity it is lower. The settling of water vapor from the air onto the surface of the product promotes the proliferation of microorganisms.
When the water content in the medium decreases, the growth of microorganisms slows down and may stop completely. Therefore, dry foods can be stored much longer than foods with high humidity. Drying food allows you to keep food at room temperature without refrigeration.
Some microbes are very resistant to drying; some bacteria and yeasts can survive in a dried state for up to a month or more. Spores of bacteria and molds remain viable in the absence of moisture for tens and sometimes hundreds of years.
Temperature
Temperature is the most important factor for the development of microorganisms. For each microorganism there is a minimum, optimum and maximum temperature regime for growth. Based on this property, microbes are divided into three groups:
- psychrophiles - microorganisms that grow well at low temperatures with a minimum at -10-0 °C, optimum at 10-15 °C;
- mesophiles - microorganisms for which optimum growth is observed at 25-35 °C, minimum at 5-10 °C, maximum at 50-60 °C;
- thermophiles - microorganisms that grow well at relatively high temperatures with optimum growth at 50-65 °C, maximum at temperatures above 70 °C.
Most microorganisms are mesophiles, for which the optimal temperature is 25-35 °C. Therefore storage food products at this temperature leads to the rapid proliferation of microorganisms in them and spoilage of products. Some microbes, when significantly accumulated in products, can lead to food poisoning person. Pathogenic microorganisms, i.e. causing infectious diseases in humans are also classified as mesophiles.
Low temperatures slow down the growth of microorganisms, but do not kill them. In refrigerated foods, microbial growth is slow but continues. At temperatures below 0°C, most microbes stop reproducing, i.e. When food is frozen, the growth of microbes stops, some of them gradually die off. It has been established that at temperatures below 0 °C, most microorganisms enter a state similar to anabiosis, retain their viability, and continue their development as the temperature rises. This property of microorganisms should be taken into account during storage and further culinary processing of food products. For example, salmonella can persist in frozen meat for a long time, and after defrosting the meat, under favorable conditions, they quickly accumulate to an amount dangerous to humans.
When exposed to high temperatures exceeding the maximum endurance of microorganisms, they die. Bacteria that do not have the ability to form spores die when heated in a humid environment to 60-70 ° C in 15-30 minutes, to 80-100 ° C in a few seconds or minutes. Bacterial spores have much higher heat resistance. They are able to withstand 100 °C for 1-6 hours; at a temperature of 120-130 °C, bacterial spores in a humid environment die after 20-30 minutes. Mold spores are less heat resistant.
Thermal culinary processing of food products in public catering, pasteurization and sterilization of products in Food Industry lead to partial or complete (sterilization) death of vegetative cells of microorganisms.
During pasteurization, the food product is exposed to minimal temperature effects. Depending on the temperature regime, low and high pasteurization are distinguished.
Low pasteurization is carried out at a temperature not exceeding 65-80 ° C, for at least 20 minutes to better guarantee the safety of the product.
High pasteurization is a short-term (no more than 1 minute) exposure of the pasteurized product to a temperature above 90 °C, which leads to the death of pathogenic non-spore-bearing microflora and at the same time does not entail significant changes in the natural properties of the pasteurized products. Pasteurized foods cannot be stored without refrigeration.
Sterilization involves freeing the product from all forms of microorganisms, including spores. Sterilization of canned food is carried out in special devices - autoclaves (under steam pressure) at a temperature of 110-125 ° C for 20-60 minutes. Sterilization provides the possibility of long-term storage of canned food. Milk is sterilized using ultra-high temperature treatment (at temperatures above 130 ° C) for a few seconds, which allows you to preserve all beneficial features milk.
Environment reaction
The vital activity of microorganisms depends on the concentration of hydrogen (H +) or hydroxyl (OH -) ions in the substrate on which they develop. For most bacteria, a neutral (pH about 7) or slightly alkaline environment is most favorable. Molds and yeasts grow well in a slightly acidic environment. A highly acidic environment (pH below 4.0) inhibits the growth of bacteria, but mold can continue to grow in a more acidic environment. Suppression of the growth of putrefactive microorganisms when the environment is acidified has practical use. The addition of acetic acid is used when pickling foods, which prevents rotting processes and allows food to be preserved. The lactic acid formed during fermentation also inhibits the growth of putrefactive bacteria.
Salt and sugar concentration
Table salt and sugar have long been used to increase the resistance of foods to microbial spoilage and to better preserve food products.
Some microorganisms require high salt concentrations (20% or higher) for their development. They are called salt-loving, or halophiles. They can cause spoilage of salty foods.
High concentrations of sugar (above 55-65%) stop the proliferation of most microorganisms; this is used when preparing jam, marmalade or marmalade from fruits and berries. However, these products can also be spoiled by the growth of osmophilic molds or yeasts.
Light
Some microorganisms require light for normal development, but for most of them it is harmful. The ultraviolet rays of the sun have a bactericidal effect, that is, at certain doses of radiation they lead to the death of microorganisms. The bactericidal properties of ultraviolet rays of mercury-quartz lamps are used to disinfect air, water, and some food products. Infrared rays can also cause the death of microbes due to thermal effects. Exposure to these rays is used in the heat treatment of products. Electromagnetic fields, ionizing radiation and other physical environmental factors can have a negative impact on microorganisms.
Chemical factors
Some chemicals can have a detrimental effect on microorganisms. Chemicals that have a bactericidal effect are called antiseptics. These include disinfectants (bleach, hypochlorites, etc.) used in medicine, in the food industry and public catering.
Some antiseptics are used as food additives (sorbic and benzoic acids, etc.) in the production of juices, caviar, creams, salads and other products.
Biological factors
The antagonistic properties of some are explained by their ability to release substances into the environment that have an antimicrobial (bacteriostatic, bactericidal or fungicidal) effect - antibiotics. Antibiotics are produced mainly by fungi, less often by bacteria, they exert their specific effect on certain types of bacteria or fungi (fungicidal effect). Antibiotics are used in medicine (penicillin, chloramphenicol, streptomycin, etc.), in animal husbandry as a feed additive, in the food industry for food preservation (nisin).
Phytoncides, substances found in many plants and foods (onions, garlic, radishes, horseradish, spices, etc.), have antibiotic properties. Phytoncides include essential oils, anthocyanins and other substances. They are capable of causing the death of pathogenic microorganisms and putrefactive bacteria.
Egg whites, fish roe, tears, and saliva contain lysozyme, an antibiotic substance of animal origin.
Federal State Educational Institution of Higher Professional Education
"Moscow state academy veterinary medicine and biotechnology named after"
_____________________________________________________
Influence of physical, chemical and biological factors
on microorganisms
Moscow – 2011
Gryazneva physical, chemical and biological factors on microorganisms / Lecture. - M.: Federal State Educational Institution of Higher Professional Education MGAVMiB. - 20 p.
Intended for students of higher educational institutions in the specialties 111801 - “Veterinary Science”, 020207 - “Biophysics”, 020208 - “Biochemistry”, 110501 – “Veterinary Sanitary Expertise”, 080 – “Commodity Science and Expertise of Goods”, 111100 – “Animal Science”.
Reviewers:
Doctor of Veterinary Sciences, Professor
Approved by the educational, methodological and clinical commission of the Faculty of Veterinary Medicine of the Federal State Educational Institution of Higher Professional Education MGAVMiB (protocol dated March 21, 2011).
Influence of physical, chemical and biological factors on microorganisms
Introduction.
1. Physical factors affecting microorganisms.
2. Chemical factors.
3. Biological factors.
4. Sterilization.
5. Adaptability of microorganisms to unfavorable environmental factors.
Conclusion.
Questions for self-control
Literature
1. , Burlakova G.I., Shaikova preparation of students in the discipline “Microbiology” with test tasks: Textbook. – M.: Federal State Educational Institution of Higher Professional Education MGAVMiB, 2008.
2. , Rodionova //Methodological recommendations for studying the discipline and performing independent work for students of the Faculty of Veterinary Medicine full-time, part-time and part-time study. - M.: Federal State Educational Institution of Higher Professional Education MGAVMiB. - 2008.
3., Gosmanov microbiology and immunology: Textbook. - M.: Kolos. - 2006.
4., Skorodumov meeting on veterinary microbiology. - M.: Kolos. - 2008.
5. Pozdeev microbiology: Textbook for universities. - M.: Geotar-Med. - 2001.
6., Bannikov morphology of populations of pathogenic bacteria. - M.: Kolos. 2007.
Introduction
The life of microorganisms is closely dependent on environmental conditions, so microorganisms must constantly adapt to it.
Both humans, animals and plants, and microorganisms are significantly influenced by various environmental factors. They can be divided into three groups: physical, chemical and biological.
Antimicrobial environmental factors |
Physical | Chemical | Biological |
Results of the action of environmental factors on microorganisms:
1. Favorable.
2. Unfavorable (bacteriostatic and bactericidal effects).
3. Changing properties of microorganisms.
4. Indifferent.
Antimicrobial environmental factors are used in sterilization, disinfection, treatment, compliance with the rules of asepsis and antisepsis, etc.
1. Physical factors affecting microorganisms
Of the physical factors, the greatest influence on microorganisms is exerted by:
1. Temperature.
2. Drying (freeze drying).
3. Radiant energy (microwave energy, ultraviolet rays, ionizing radiation).
4. Ultrasound.
5. Pressure (atmospheric, hydrostatic, osmotic).
6. Electricity.
7. Acidity of the environment (pH of the environment).
8. Availability of oxygen.
9. Humidity and viscosity of the habitat.
Temperature - one of the most powerful factors affecting microorganisms. They either survive or die, or adapt and grow.
Effects of temperature on bacteria:
1. The ability of microorganisms to survive after prolonged exposure to extreme temperature conditions.
2. The ability of microorganisms to grow under extreme temperature conditions.
The life activity of each microorganism is limited by certain temperature limits.
This temperature dependence usually expressed in three dots:
§ minimum (min) temperature - below which reproduction stops;
§ optimal (opt) temperature - the best temperature for the growth and development of microorganisms;
§ maximum (max) temperature - the temperature at which cell growth either slows down or stops completely.
The optimal temperature is usually equal to the ambient temperature.
All microorganisms in relation to temperature can be divided into 3 groups: psychrophiles, mesophylls, thermophiles.
Saprophytes
Yersinia
Pseudomonas
Klebsiella
Listeria, etc.
Optimal temperature for growth and reproduction of psychrophiles
Psychrophiles- these are cold-loving microorganisms that grow at low temperatures: min t - 0°C, opt t - from 10-20°C, max t - up to 35°C. Such microorganisms include inhabitants of the northern seas and reservoirs, as well as some pathogenic bacteria - causative agents of yersiniosis, pseudomonosis, klebsiellosis, listeriosis, etc.
Many microorganisms are very resistant to low temperatures. For example, listeria, cholera vibrio, and some types of Pseudomonas atrobacter can be stored in ice for a long time without losing their viability.
Some microorganisms can withstand temperatures down to minus 190°C, and bacterial spores can withstand temperatures up to minus 250°C. The action of low temperatures stops putrefactive and fermentation processes, which is why we use refrigerators in everyday life.
At low temperatures, microorganisms enter a state of suspended animation, in which all vital processes occurring in the cell slow down. However, many of the psychrophiles are capable of quickly causing microbial spoilage of food and feed stored at 0°C.
Most pathogenic and opportunistic microorganisms
Optimal temperature for growth and reproduction of mesophiles
Mesophiles- this is the most extensive group of bacteria, which includes saprophytes and almost all pathogenic microorganisms, since the opt temperature for them is 37°C (body temperature), min t - 10°C, max t - 50°C.
Thermophiles- heat-loving bacteria, develop at temperatures above 55°C, min t for them is 40°C, max t – up to 100°C. These microorganisms live mainly in hot springs. Among thermophiles there are many spore forms (B. stearothermophilus. B. aerothermophilus) and anaerobes.
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Vegetative forms Spores
Temperature ranges for the death of microorganisms
Bacterial spores are much more resistant to high temperatures than vegetative forms of bacteria. For example, anthrax bacillus spores can withstand boiling for 2 hours.
All microorganisms, including spores, die at a temperature of 165-170°C for 1 hour.
The effect of high temperatures on microorganisms is the basis of sterilization.
Drying. For the normal functioning of microorganisms, water is needed. Drying leads to dehydration of the cytoplasm and the integrity of the cytoplasmic membrane is disrupted, which leads to cell death.
Some microorganisms (many types of cocci) die after drying within a few minutes.
Tuberculosis pathogens, which can remain viable for up to 9 months, as well as capsule forms of bacteria are more resistant to drying.
Spores are especially resistant to drying. For example, anthrax spores can survive in soil for more than 100 years.
For the storage of microorganisms in microbial culture museums and the production of dry vaccine preparations from bacteria, the method freeze drying.
The essence of the method is that in apparatus for freeze drying - lyophilizers, microorganisms are first frozen and then dried at a positive temperature under vacuum conditions. In this case, the cytoplasm of the bacteria freezes and turns into ice, and then this ice evaporates and the cell remains alive (the transition of water from a frozen state to a gaseous state, bypassing the liquid phase - sublimation).
Frozen bacteria (Ifreeze-drying stage)
Extracellular formation(A) and intracellular(b) ice for freeze-drying bacteria
Freeze-dried diplococci
With proper freeze-drying, microbial cells enter a state of suspended animation and retain their biological properties for several years.
Freeze-dried live(A) and deceased(b) bacteria
If the freeze-drying regime was not followed (and for different types bacteria, it is different), then the cell wall of the bacteria breaks and they die.
Radiant Energy. There are different forms of radiant energy, characterized by different properties, strength and nature of action on microorganisms.
In nature, bacterial cells are constantly exposed to solar radiation.
Direct sunlight has a detrimental effect on microorganisms. This refers to the ultraviolet spectrum of sunlight (UV rays).
Plants Photosynthesis Phototropism Photoperiodism | Bacteria Phototaxis Mutations Bactericidal action | Animals and humans Photoerythema Photodynamics |
Due to the inherent high chemical and biological activity of UV rays, they cause inactivation of enzymes in microorganisms, coagulation of proteins, and destroy DNA, resulting in cell death. In this case, only the surface of irradiated objects is disinfected due to the low penetrating ability of these rays.
Pathogenic bacteria are more sensitive to the action of UV rays than saprophytes, so in a bacteriological laboratory microorganisms are grown and stored in the dark.
Buchner's experience shows how UV rays have a detrimental effect on bacteria: a Petri dish with a dense medium is seeded with a continuous lawn. Part of the crop is covered with paper, and the Petri dish is placed in the sun, and then after some time (15-30 minutes) it is placed in a thermostat.
Only those microorganisms that were under the paper germinate. Therefore, the importance of sunlight for environmental disinfection is very great.
Ultrasound-emitting devices used for these purposes are called ultrasonic disintegrators (USD).
High pressure. Bacteria, and especially spores, are very resistant to high atmospheric or hydrostatic pressure (barophilic microorganisms). In nature, there are bacteria that live in the seas and oceans at a depth of m under pressure from 100 to 900 atm. These bacteria are saprophytic and belong to archaea.
Bacteria tolerate pressure of atm, and bacterial spores - up to 20,000 atm. At such high pressure, the activity of bacterial enzymes and toxins decreases.
The combined action of elevated temperatures and elevated pressure is used in steam sterilizers (autoclaves) for sterilization with steam under pressure.
An important factor is intracellular osmotic pressure in various microorganisms.
The effect of osmotic pressure on a microbial cell:
1. Plasmolysis (loss of water and cell death) occurs with microorganisms if they are placed in an environment with higher osmotic pressure.
2. Plasmoptysis (water entering the cell and rupture of the cell wall) - occurs with microorganisms when they move into an environment with low osmotic pressure.
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For acidophiles, the optimal pH for life is -6.0-7.0; for alkalophiles - 9.0-10.0; for neutralophiles - 7.5.
The pH value has a significant impact on the synthesis of a particular metabolite.
In some cases, the optimum for crop growth and product formation is not the same. As the cultivation temperature increases, the range of tolerable pH values narrows.
Medium viscosity determines the diffusion of nutrients from the volume of the medium to the cell surface.
2. Chemical factors
It is known that changes in the composition and concentration of nutrients in the nutrient medium can slow down, stop or stimulate the processes of growth and reproduction of the bacterial population. Consequently, chemical factors can influence the life activity of microorganisms.
The degree of influence of a chemical agent on a microorganism may vary. It depends on the chemical compound, its concentration, duration of exposure, as well as on the individual properties of the microorganism.
Bacteriostatic effect is registered if a chemical substance inhibits the reproduction of bacteria, and after its removal the reproduction process is restored.
Bactericidal effect causes irreversible death of microorganisms.
Some chemicals are indifferent to bacteria, others can stimulate their development processes or provide food for bacteria. For example, NaCl salt is added in small quantities to culture media.
Chemicals that can have a bactericidal effect on different groups of microorganisms are used for disinfection.
Disinfection(destruction of infection, disinfection of environmental objects) is a set of measures aimed at destroying pathogens of infectious diseases in environment.
In other words, disinfection– is the destruction of pathogenic microorganisms in the external environment using chemicals that have an antimicrobial effect.
Chemicals acting on microorganisms include:
1. Oxidizing agents.
2. Surfactants.
3. Halogens.
4. Salts heavy metals.
5. Acids.
6. Alkalis.
7. Alcohols.
8. Phenols, cresols and their derivatives.
9. Aldehydes (formaldehyde, formalin).
10. Dyes.
By mechanism of antimicrobial action all chemicals are divided into 5 classes:
1. Denaturing proteins - coagulate and fold proteins.
2. Saponifying proteins – lead to swelling and dissolution of proteins.
3. Oxidizing proteins - damage the sulfhydryl groups of active proteins.
4. Reacting with phosphate groups of nucleic acids.
5. Surfactants - cause damage to the cell wall.
Denaturing substances:
§ phenol, cresol and their derivatives - the bactericidal effect is associated with damage to the cell wall and denaturation of cytoplasmic proteins;
§ formaldehyde - bactericidal effect is due to dehydration of surface layers and protein denaturation;
§ alcohols - the bactericidal effect is due to the ability to take away water and coagulate proteins;
§ salts of heavy metals (sublimate, merthiolate, salts of mercury, silver, zinc, lead, copper) - positively charged metal ions are adsorbed on the negatively charged surface of bacteria and change the permeability of their cytoplasmic membrane, while the structure of respiratory enzymes changes and the processes of oxidation and phosphorylation are uncoupled in mitochondria.
Saponifying proteins – alkalis, slaked lime.
Oxidizing proteins(chlorine, bromine, iodine-containing, hydrogen peroxide, potassium permanganate) - release active atomic oxygen, causing a chain reaction of free radical lipid peroxidation, which leads to the destruction of membranes and proteins of microorganisms.
Surfactants(fatty acids, soaps, detergents, detergents) - change the energy ratio of the surface of the microbial cell (the charge changes from negative to positive), which disrupts permeability and osmotic balance.
Halogens(chlorine-containing: bleach, chloramine B, dichlor-1, sulfochloranthine, chlorcin, etc.; iodine-containing: alcohol solution of iodine, iodinol, iodoform, Lugol's solution, etc.) – destroy enzymatic structures bacterial cell, inhibit the hydrolytic and dehydrogenase activity of bacteria, inactivate enzymes such as amylases and proteases, denature cytoplasmic proteins, and also release atomic oxygen, which has an oxidizing effect on microorganisms.
Dyes(brilliant green, rivanol, trypoflavin, methylene blue) - have an affinity for phosphoric acid groups of nucleic acids and disrupt the process of bacterial division. Many dyes are used in antiseptics.
Bactericidal effect acids(salicylic, boric) and alkalis(caustic soda) on microorganisms is determined by:
§ dehydration of microorganisms;
§ changing the pH of the environment;
§ formation of acid and alkaline albuminates.
A new generation of disinfectants are quaternary ammonium compounds (QACs) and their salts.
One of the most effective disinfectants today is Veltolen - a liquid concentrate based on the unique domestic, patented substance “Welton” (QAC clathrate with urea).
Veltolen has bactericidal, fungicidal, sporicidal and virucidal effects in low concentrations, is harmless to animals and humans, and is environmentally friendly.
Mechanisms of antimicrobial action of Veltolene
Antimicrobial effect of a 0.5% Veltolen solution on the anthrax pathogen B. anthracis with an exposure of 5 minutes. causes vacuolization of the bacterial cytoplasm and detachment of the cell wall.
onB.Anthraciswith exposure 5 min.
Antimicrobial effect of 0.5% Veltolen solution on the Siberian pathogen with an exposure of 15 minutes. causes detachment of the cell wall, its rupture and vacuolization of the cytoplasm.
Antimicrobial effect of 0.5% Veltolen solution
onB.Anthraciswith exposure 15 min.
Antimicrobial effect of 0.5% Veltolen solution on the Siberian pathogen with an exposure of 60 minutes. causes the destruction of most bacterial cells with loss of the cell wall and the release of cellular detritus. Some of the spores under the influence of Veltolen form myelin figures.
Antimicrobial effect of 0.5% Veltolen solution
onB.Anthraciswith exposure 60 min.
The activity of different disinfectants is not the same and depends on exposure time, concentration, temperature of disinfectant solutions and the environment.
Disinfection using chemical substances as a component it is included in a set of measures aimed at destroying microorganisms not only in the environment, but also in the macroorganism, for example, in a wound, and is the basis of asepsis and antiseptics.
Asepsis is a set of preventive measures aimed at preventing the entry of microorganisms into a wound or the body of humans and animals.
Antiseptics- this is a set of measures aimed at destroying microorganisms in a wound or in the body as a whole, at preventing and eliminating the inflammatory process.
Antiseptics are antimicrobial substances that are used to disinfect biological surfaces.
Antiseptic chemicals include dyes (methylene blue, brilliant green) - they have a denaturing and lytic effect, and derivatives of 8-hydroxy-quinoline (quinosol, nitroxaline, quinolone) and nitrofuran (furatsilin, furazolidone), which disrupt the biosynthetic and enzymatic processes in bacterial cage.
3. Biological factors
TO biological factors, which negatively affect microorganisms include:
§ microorganisms-antagonists;
§ probiotics;
§ bacteriophages;
§ protective factors of the body (cellular and humoral).
A huge number of different types of microorganisms live in the external environment and in the body of humans and animals, which interact with each other in different ways.
Lactic acid bacteria
Predation- an attack by one type of bacteria on another with the aim of using the other species as food.
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Bdellovibrio bacteriovoruspenetrates salmonella
Neutralism– microorganisms do not have any effect on each other.
Of greatest interest to science and practice are various biologically active substances formed during the life of microorganisms, and one of them is antibiotics.
Antibiotics- metabolic products of living organisms or their analogues, obtained synthetically, capable of selectively inhibiting the growth of microorganisms.
The term "antibiotic" was proposed by V. Vuymin in 1889 to designate the active agent of the process of "antibiosis", i.e., resistance offered by one living organism to another.
In 1929, A. Fleming discovered penicillin, which was isolated in crystalline form in 1940.
The mechanism of action of antibiotics on bacteria
Classification of antibiotics
According to biological origin | According to the mechanism of biological action | According to the spectrum of biological whose actions | By chemical structure |
Eubacteria Genus Pseudomonas: pyocyanin, viscosine. | Inhibits cell wall synthesis (penicillins, cephalosporins) | Narrow spectrum (penicillins, cephalosporins) | Acyclic compounds (mycosamine, pyrosamine) |
actinomycetes Genus Streptomyces: tetracyclines, streptomycins, erythromycin. Genus Micromono-spora: gentamicins, sizomycin. | Disturbs the function of membranes (nystatin, candicidin) | Broad spectrum (tetracyclines, chloramphenicol, gentamicin, tobramycin) | Alicyclic compounds (actidione, thuic acid). Tetracyclines |
Cyanobacteria (malingolide) | Suppresses RNA synthesis (kanamycin, neomycin) and DNA synthesis (actidione, edeine) | Antituberculosis (streptomycin, kanamycin) | Aromatic compounds (gallic acid, chloramphenicol). |
Mushrooms (penicillins) | Inhibitors of purine and pyrimidine synthesis (azaserine) | Antifungals (nystatin, candicin) | Oxygen-containing heterocyclic compounds (penicillic acid, carline oxide) |
Lichens, plants, algae(usnic acid, chlorellin) | Suppresses protein synthesis (kanamycin, tetracyclines, erythromycin, chloramphenicol) | Antitumor (adriamycin) | Macrolides (erythromycin) |
Animal origin (interferon, ecmolin) | Respiratory inhibitors (usnic acid, pyocyanin). Inhibitors of oxidative phosphorylation (valinomycin, oligomycin) | Antimoebic (fumagillin) | Aminoglycosides (tobramycin, gentamicin, streptomycins). Polypeptides (gramicidins) |
“Pearl necklace phenomenon” in the anthrax pathogen when grown on a nutrient medium with penicillin
As a result of the action of penicillin on B. anthracis, the cell wall of the pathogen is destroyed and spherical protoplasts are formed, connected to each other in the form of a string of beads.
Penicillin can cause cell wall destruction in many types of bacteria. Until recently, staphylococci and streptococci were especially sensitive to it.
Most gram-negative bacteria have developed resistance to penicillin due to their ability to synthesize the enzyme penicillinase, which destroys penicillin.
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Possible mechanisms of action of probiotics:
1. Suppression of living pathogenic and opportunistic microorganisms.
a) production of antibacterial substances - bacteriocins;
b) competition for food sources;
c) competition for adhesion receptors.
2. Effect on microbial antagonism.
a) decrease in enzymatic activity;
b) increase in enzymatic activity.
3. Stimulation of immunity.
b) increased activity of macrophages.
Probiotic preparations produced in countries –
EU members and the types of microorganisms used in them
A drug | Type of microorganisms |
Liquid acidophilus milk, yoghurt products (everywhere) | L. acidophilus, B. bifidum, B. longum |
Biograd, Beefyogurt Yoga-Line, Lactopriv, Eugalin, Vitacidophilus, Omniflora Mutaflor, Kolivit, Symbioflor, Lactana-B (Germany) | L. acidophilus, S. thermophilus, B. longum, B. bifidum, E. coli |
Gefilak, Baktolak (Finland) | L. rhamnosum, L. casei, S. faecium |
Yocult, Bifider, Toyocerin, Lacris, Graugen, Calsporin, Miarizan, Korolak, Biofermin, Balantol, Lactofed (Japan) | L. rhamnosum, L. casei, E. coli, B. cereus, L. sporogenes, B. subtilis, B. thermophilus, C. butyricum, B. pseudolongum, S. faecalis, L. acidophilus, B. toyo |
Biokos (Czech Republic) | B. bifidum, L. acidophilus, P. acidilactis |
Sinelak, Orthobacter, Bifidigen, Liobifidus, Probiomin, Normoflor, Biolactal (France) | L. bulgaricus, L. acidophilus, B. longum E. coli, S. thermophilus, B. bifidum |
Infloran (Switzerland) | S. thermophilus, L. bulgaricus, L. acidophilus |
Pioneer (Spain) | Complex of intestinal microflora |
Ventrax ocido (Sweden) | L. acidophilus, S. faecium, S. thermophilus |
Gastrofarm, Normoflor (Bulgaria) | L. acidophilus, L. bulgaricus |
Bio-Plus2 (Germany, Denmark) | B. subtilis, B. licheniformis |
Proteksin, Pripalak (Holland) | |
Baktisubtil (Yugoslavia) | |
Acid-Pak-4-Way, Lacto-Sac (USA) | S. thermophilus, L. acidophilus |
In addition to the listed types of bacteria, in a number of countries Saccaharomyces cerevisiae, Candida pintolopesii, Aspergillus niger and Aspergillus orysae are used in probiotics for animals.
Lactic acid bacteria commonly used to produce probiotics include lactic acid streptococci (S. lactis and S. cremoris) and lactobacilli (L. acidophilum, L. casei, L. plantarum, L. bulgaricum).
Metabolites of lactic acid bacteria and their regulatory functions
Mechanism of action | Biological effect |
Lactic acid |
|
Synergism of combination with acetic, propionic, butyric acids. Synthesis of intracellular and extracellular lactoferrin. | Inhibition of the growth of pathogenic microorganisms. Reduced synthesis of toxins by mold fungi in feed. |
Carbon dioxide |
|
Maintaining anaerobic conditions and high partial pressure. | Decreased respiratory potential in aerobic intestinal bacteria. |
Hydrogen peroxide |
|
Formation of hypothiocynate in bacteria. Depletion of the enzyme system in catalase-dependent microorganisms. Inactivation of cellular enzymes. | Toxic effect on catalase-positive microflora. Reduced protein synthesis, limited transmission of genetic information, decreased adhesion factors in gram-negative bacteria. |
Binding of antilysozyme factor in enteropathogenic bacteria. Lysis of bacterial cell walls. | Increased phagocytic activity of macrophages. Reduced colonization activity in gram-negative bacteria. Nonspecific stimulation of macrophages. |
Bacteriocins |
|
Limitation of protein synthesis. Disruption of transport processes across the cell membrane, decreased DNA synthesis, compaction of nuclear material, changes in ribosomes and lysosomes. | Bactericidal and bacteriostatic action. Inhibition of bacterial division processes, disruption of the transmission of hereditary information. Destruction of receptor connections. |
In Russia, pure cultures of lactic acid bacteria have been used since 1890. A great contribution to the development of methods for preparing pure cultures, preserving them in dry form and using them in the production of fermented milk products was made by and.
Dry heat sterilization- carried out in Pasteur ovens (dry-heat oven). It is a double-walled cabinet made of metal and asbestos, heated by electricity and equipped with a thermometer. Dry heat is used to sterilize mainly laboratory glassware. Disinfection of the material in it occurs at 160°C for 1 hour.
In bacteriological laboratories, this type of sterilization is used: calcination over fire (filling). This method is used to disinfect bacteriological loops, spatulas, and pipettes. For calcination over a fire, use alcohol lamps or gas burners.
Physical methods of sterilization also include UV rays And x-ray radiation . Such sterilization is carried out in cases where the objects being sterilized cannot withstand high temperatures.
Tyndalization(two-stage sterilization) is used to disinfect material contaminated with bacterial spores. In this case, two modes of heating the material are used - the first mode is optimal for the germination of spores and the transition of the spore form of bacteria to the vegetative one, and the second mode is aimed at destroying the vegetative cells of microorganisms.
Mechanical sterilization(filter sterilization) - carried out using filters (ceramic, glass, asbestos) and especially membrane ultrafilters made from colloidal solutions of nitrocellulose.
Morphology" href="/text/category/morfologiya/" rel="bookmark">morphology (rounding, elongation of the cell), cultural properties (staphylococci do not form pigment in the absence of oxygen), biochemical or enzymatic properties (production of adaptive enzymes in Escherichia - enzyme lactase on a medium with lactose).With phenotypic variability, as a rule, after a certain time there is a return to the original state (the “new phenotype” is lost).
2. Genotypic variability(heritable) - occurs as a result of mutations and genetic recombinations. In this case, a change in phenotype is associated with a change in genotype and is inherited. There is no return to the original phenotype.
Mutations(from Latin mutatio - to change) are structural changes in genes that are persistently inherited and associated with the reorganization of nucleotides in the DNA molecule. Mutations change sections of genomes (i.e., the hereditary apparatus).
Bacterial mutations can be spontaneous (spontaneous) and induced (directed), i.e., they appear as a result of the treatment of microorganisms with special mutagens (chemicals, temperature, radiation, etc.).
As a result of bacterial mutations, the following may occur:
§ changes in the morphological properties of microorganisms;
§ change in cultural properties;
§ emergence of drug resistance in microorganisms;
§ weakening of pathogenic properties, etc.
TO genetic recombinations include gene recombinations that occur as a result of transformation, transduction and conjugation.
Transformation-transfer of genetic material from a donor bacterium to a recipient bacterium using isolated DNA from another cell.
Bacteria that can perceive the DNA of another cell are called competent.
The state of competence often coincides with the logarithmic phase of growth.
For transformation, it is necessary to create special conditions, for example, when inorganic phosphates are added to the nutrient medium, the frequency of transformation increases.
Transduction is the transfer of hereditary material from a donor bacterium to a recipient bacterium by a bacteriophage.
For example, using a bacteriophage, it is possible to reproduce flagella transduction, enzymatic properties, antibiotic resistance, toxigenicity and other characteristics.
Conjugation- transfer of genetic material from one bacterium to another through direct contact. Moreover, a one-way transfer of genetic material occurs - from the donor to the recipient. A necessary condition for conjugation is the presence in the donor of a cytoplasmic circular DNA molecule - a plasmid and a specific fertility factor F. In gram-negative bacteria, reproductive F-hairs are found, through which the transfer of genetic material occurs. Cells playing the role of donor are designated F+, and recipient cells are designated F–-.
3. Intermediate variability - dissociation. In a homogeneous population of bacteria, cells with different biological properties appear, forming two forms of colonies - R (rough, with torn edges, often associated with the acquisition of pathogenic properties by bacteria) and S (round, smooth, shiny).
Conclusion
Microorganisms in the external environment are affected by a huge number of different unfavorable factors, which forces them to constantly improve, adapt and evolve.
It is unfavorable environmental factors that are the driving force behind speciation for microorganisms.
Questions for self-control
1. Results of the action of environmental factors on microorganisms.
2. What physical factors have the greatest influence on microorganisms?
3. What is the temperature range for growing different types of microorganisms?
4. What is the essence of freeze-drying of microorganisms?
5. Describe Buchner's experience.
6. The value of osmotic pressure for bacteria.
7. What groups are microorganisms classified into in relation to the concentration of hydrogen ions in the environment?
8. What are disinfection and disinfectants?
9. Classification of chemicals according to the mechanism of antimicrobial action.
10. What products are called antiseptics?
11. List the biological factors that negatively affect microorganisms.
12. What relationships between bacteria are caused by antagonistic symbiosis?
13. What is the mechanism of action of antibiotics on bacteria?
14. Name the possible mechanisms of action of probiotics.
15. What groups are bacteriophages divided into?
16. What is filter sterilization?
17. Name the differences between phenotypic and genotypic variability of bacteria.
Lecture No. 10
Dictionary
RAW MATERIALS – raw materials intended for further processing. Medicinal raw materials.
MAZE – monitor grazing livestock and domestic animals; noun Grazing.
CORK - close tightly, plug up.
FAD – wither. Flowers fade .
Dwarf – the plant is unnaturally small in stature.
POISON – poisonous substance .
WASH – wash away, wash away, noun. Flush .
SHOCK – severe impairment of body functions due to physical injury ;
WIGGLE ( set in motion) - rock slightly.
FAST ≠ SLOW.
Influence of environmental factors on microorganisms. Sterilization. Methods and equipment. Sterilization quality control. The concept of disinfection, asepsis and antiseptics.
Microorganisms are influenced by physical, chemical and biological environmental factors. Physical factors: temperature, radiant energy, drying, ultrasound, pressure, filtration. Chemical factors: reaction of the environment (pH), substances of different nature and concentration. Biological factors– this is the relationship of microorganisms with each other and with the macroorganism, the influence of enzymes and antibiotics.
Environmental factors can affect microorganisms beneficial effect(growth stimulation) and bad influence : microbicidal action (destructive) and microbostatic action (growth suppression), as well as mutagenic action.
The effect of temperature on microorganisms.
Temperature is an important factor influencing the life activity of microorganisms. For microorganisms, there are minimum, optimal and maximum temperatures. Optimal– the temperature at which the most intensive proliferation of microbes occurs. Minimum– temperature below which microorganisms do not exhibit vital activity. Maximum– the temperature above which the death of microorganisms occurs.
In relation to temperature, 3 groups of microorganisms are distinguished:
2. Mesophiles. Optimum – 30-37°С. Minimum – 15-20°C. Maximum – 43-45°C. They live in the bodies of warm-blooded animals. These include most pathogenic and opportunistic microorganisms.
3. Thermophiles. Optimum – 50-60°C. Minimum - 45°C. Maximum - 75°С. They live in hot springs and participate in the processes of self-heating of manure and grain. They are not able to reproduce in the body of warm-blooded animals, so they have no medical significance.
Favorable action optimal temperature used in growing microorganisms for the purpose of laboratory diagnostics, preparation of vaccines and other drugs.
Braking action low temperatures used for storage products and cultures of microorganisms in a refrigerator. Low temperature stops putrefactive and fermentation processes. The mechanism of action of low temperatures is the inhibition of metabolic processes in the cell and the transition to a state of suspended animation.
Detrimental effect high temperature (above maximum) used for sterilization . Mechanism actions – denaturation of protein (enzymes), damage to ribosomes, disruption of the osmotic barrier. Psychrophiles and mesophiles are most sensitive to high temperatures. special stability show disputes bacteria.
The effect of radiant energy and ultrasound on microorganisms.
There are non-ionizing (ultraviolet and infrared rays of sunlight) and ionizing radiation (g-rays and high-energy electrons).
Ionizing radiation has a powerful penetrating effect and damages the cellular genome. Mechanism damaging effect: ionization macromolecules, which is accompanied by the development of mutations or cell death. Moreover, lethal doses for microorganisms are higher than for animals and plants.
Mechanism damaging effect UV rays: formation of thymine dimers in a DNA molecule , which stops cell division and is the main cause of their death. The damaging effect of UV rays is more pronounced for microorganisms than for animals and plants.
Ultrasound(sound waves 20 thousand Hz) has a bactericidal effect. Mechanism: education in the cytoplasm of the cell cavitation cavities , which are filled with liquid vapor and a pressure of up to 10 thousand atm arises in them. This leads to the formation of highly reactive hydroxyl radicals, to the destruction cellular structures and depolymerization of organelles, denaturation of molecules.
Ionizing radiation, UV rays and ultrasound are used for sterilization.
Effect of drying on microorganisms.
Water is necessary for the normal functioning of microorganisms. A decrease in environmental humidity leads to the transition of cells to a state of rest, and then to death. Mechanism detrimental effects of drying: dehydration of the cytoplasm and denaturation of proteins.
Pathogenic microorganisms are more sensitive to drying: pathogens of gonorrhea, meningitis, typhoid fever, dysentery, syphilis, etc. Bacterial spores, protozoan cysts, bacteria protected by sputum mucus (tuberculosis bacilli) are more resistant.
In practice drying is used for canning meat, fish, vegetables, fruits, when preparing medicinal herbs.
Drying from frozen state under vacuum – lyophilization or freeze drying. She's being used for crop conservation microorganisms that in this state for years (10-20 years) do not lose their viability and do not change their properties. Microorganisms are in a state of suspended animation. Lyophilization is used in the production of drugs from living microorganisms: eubiotics, phages, live vaccines against tuberculosis, plague, tularemia, brucellosis, influenza, etc.
The effect of chemical factors on microorganisms.
Chemicals affect microorganisms in different ways. This depends on the nature, concentration and time of action of the chemicals. They can stimulate growth(used as energy sources), provide microbicidal, microbostatic, mutagenic effect or may be indifferent to vital processes
For example: a 0.5-2% glucose solution is a source of nutrition for microbes, and a 20-40% solution has an inhibitory effect.
For microorganisms it is necessary optimal pH value of the environment. For most symbionts and pathogens of human diseases - a neutral, slightly alkaline or slightly acidic environment. As the pH increases, it often shifts to the acidic side, and the growth of microorganisms stops. And then death comes. Mechanism: denaturation of enzymes by hydroxyl ions, disruption of the osmotic barrier of the cell membrane.
Chemicals that have antimicrobial effect, used for disinfection, sterilization and preservation.
The effect of biological factors on microorganisms.
Biological factors are various forms of influence of microbes on each other, as well as the effect of immune factors (lysozyme, antibodies, inhibitors, phagocytosis) on microorganisms during their stay in the macroorganism. Coexistence of various organisms - symbiosis. The following are distinguished: forms symbiosis.
Mutualism– a form of cohabitation where both partners receive mutual benefits (for example, nodule bacteria and legumes).
Antagonism- a form of relationship when one organism causes harm (even death) to another organism with its metabolic products (acids, antibiotics, bacteriocins), due to better adaptability to environmental conditions, through direct destruction (for example, normal intestinal microflora and pathogens of intestinal infections).
Metabiosis– a form of cohabitation when one organism continues the process caused by another (uses its waste products) and frees the environment from these products. Therefore, conditions are created for further development (nitrifying and ammonifying bacteria).
Satellism– one of the cohabitants stimulates the growth of the other (for example, yeast and sarcina produce substances that promote the growth of other, more nutrient-demanding bacteria).
Commensalism– one organism lives at the expense of another (benefits) without causing harm to it (for example, E. coli and the human body).
Predation– antagonistic relationships between organisms, when one captures, absorbs and digests another (for example, intestinal amoeba feeds on intestinal bacteria).
Sterilization.
Sterilization is the process of complete destruction of all viable forms of microbes in an object, including spores.
There are 3 groups of sterilization methods: physical, chemical and physico-chemical. Physical methods: sterilization by high temperature, UV irradiation, ionizing irradiation, ultrasound, filtration through sterile filters. Chemical Methods– use of chemicals, as well as gas sterilization. Physico-chemical methods– joint use of physical and chemical methods. For example, high temperature and antiseptics.
High temperature sterilization .
This method includes: 1) dry heat sterilization; 2) steam sterilization under pressure; 3) flowing steam sterilization; 4) tindialization and pasteurization; 5) calcination; 6) boiling.
Dry heat sterilization.
The method is based on the bactericidal effect of air heated to 165-170°C for 45 minutes.
Equipment: dry heat oven (Pasteur oven). A Pasteur oven is a metal cabinet with double walls, lined on the outside with a material that does not conduct heat well (asbestos). Heated air circulates in the space between the walls and exits through special openings. When working, it is necessary to strictly monitor the required temperature and sterilization time. If the temperature is higher, then charring of cotton plugs and paper in which the dishes are wrapped will occur, and at a lower temperature, longer sterilization is required. After sterilization is completed, the cabinet is opened only after it has cooled, otherwise the glassware may crack due to a sudden change in temperature.
a) glass, metal, porcelain items, dishes, wrapped in paper and closed with cotton-gauze stoppers to maintain sterility (165-170°C, 45 min);
b) heat-resistant powdered medicines - talc, white clay, zinc oxide (180-200°C, 30-60 min);
c) mineral and vegetable oils, fats, lanolin, petroleum jelly, wax (180-200°C, 20-40 min).
Steam sterilization under pressure.
The most effective and widely used method in microbiological and clinical practice.
The method is based on the hydrolyzing effect of steam under pressure on the proteins of the microbial cell. The combined action of high temperature and steam ensures the high efficiency of this sterilization, which kills the most persistent spore bacteria.
Equipment – autoclave. The autoclave consists of 2 metal cylinders inserted into each other with a hermetically sealed lid screwed in with screws. The outer boiler is a water-steam chamber, the inner boiler is a sterilization chamber. There is a pressure gauge, steam release valve, safety valve, and water meter glass. At the top of the sterilization chamber there is a hole through which steam passes from the water-steam chamber. The pressure gauge is used to determine the pressure in the sterilization chamber. There is a certain relationship between pressure and temperature: 0.5 atm - 112°C, 1-01.1 atm - 119-121°C, 2 atm - 134°C. Safety valve – to protect against excessive pressure. When the pressure rises above the set value, the valve opens and releases excess steam. Operating procedure. Water is poured into the autoclave, the level of which is monitored using a water meter glass. The material is placed into the sterilization chamber and the lid is screwed on tightly. The steam valve is open. Turn on the heating. After the water boils, the tap is closed only when all the air has been displaced (steam flows in a continuous strong dry stream). If the tap is closed earlier, the pressure gauge readings will not correspond to the desired temperature. After closing the tap, the pressure in the boiler gradually increases. The beginning of sterilization is the moment when the pressure gauge needle shows the set pressure. After the sterilization period has expired, stop heating and cool the autoclave until the pressure gauge needle returns to 0. If you release steam earlier, the liquid may boil due to a rapid change in pressure and push out the plugs (sterility is impaired). When the pressure gauge needle returns to 0, carefully open the steam release valve, release the steam and then remove the objects to be sterilized. If the steam is not released after the needle returns to 0, water may condense and wet the plugs and the material being sterilized (sterility will be impaired).
Material and sterilization mode:
a) glass, metal, porcelain dishes, linen, rubber and cork stoppers, products made of rubber, cellulose, wood, dressings (cotton wool, gauze) (119 - 121 ° C, 20-40 min));
b) physiological solution, solutions for injections, eye drops, distilled water, simple nutrient media - MPB, MPA (119-121°C, 20-40 min);
c) mineral and vegetable oils in hermetically sealed vessels (119-121°C, 120 min);
Sterilization with flowing steam.
The method is based on the bactericidal effect of steam (100°C) against only vegetative cells.
Equipment– an autoclave with an unscrewed lid or Koch apparatus.
Koch apparatus - This is a metal cylinder with a double bottom, the space in which is 2/3 filled with water. The lid has holes for a thermometer and for steam to escape. The outer wall is lined with a material that conducts heat poorly (linoleum, asbestos). The start of sterilization is the time from the boiling of water and the entry of steam into the sterilization chamber.
Material and sterilization mode. This method sterilizes the material which cannot withstand temperatures above 100°C: nutrient media with vitamins, carbohydrates (Hiss, Endo, Ploskirev, Levin media), gelatin, milk.
At 100°C, spores do not die, so sterilization is carried out several times - fractional sterilization - 20-30 minutes daily for 3 days.
In the intervals between sterilizations, the material is kept at room temperature so that the spores germinate into vegetative forms. They will die upon subsequent heating at 100°C.
Tyndallization and pasteurization.
Tyndalization - method of fractional sterilization at temperatures below 100°C. It is used to sterilize objects, which cannot withstand 100°C: serum, ascitic fluid, vitamins . Tyndallization is carried out in a water bath at 56°C for 1 hour for 5-6 days.
Pasteurization - partial sterilization (spores are not killed), which is carried out at a relatively low temperature once. Pasteurization is carried out at 70-80°C, 5-10 minutes or at 50-60°C, 15-30 minutes. Pasteurization is used for objects that lose their quality at high temperatures. Pasteurization, for example, use For some food products: milk, wine, beer . This does not damage their commercial value, but the spores remain viable, so these products must be stored refrigerated.
The main physical factors affecting microorganisms both in their natural habitat and in the laboratory include temperature, light, electricity, drying, various types of radiation, osmotic pressure, etc.
Temperature. The effect of temperature on microorganisms is judged by their ability to grow and multiply within certain temperature limits. The optimal development temperature has been determined for each type of microorganism. Depending on the limits of this temperature, bacteria are divided into three physiological groups:
· Psychrophilic microorganisms (psychrophiles) are capable of growing and multiplying from 0 0 C to 30...35 0 C, and the temperature optimum is 15...20 0 C. Among the representatives of this group are inhabitants of the northern seas, soil, and wastewater.
· Mesophilic bacteria are capable of growing and multiplying at temperatures from 10 0 C to 40...45 0 C, the temperature optimum is 30...37 0 C. The most extensive group of microorganisms, it includes most saprophytes and all pathogenic microorganisms.
· Thermophilic bacteria - capable of growing and multiplying in temperatures ranging from 35 0 C to 70...75 0 C, the temperature optimum is 50...60 0 C. Microorganisms of this group are quite often found in nature: soil, water, warm mineral springs, the digestive tract of animals and person
· Extreme thermophilic bacteria - capable of existing at temperatures from 40 to 93 0 C and higher. The possibility of existence at high temperatures is due to the special composition of lipid components cell membranes, high thermal stability of proteins, enzymes and cellular structures.
High and low temperatures have different effects on microorganisms. At low temperatures, the cell enters a state of suspended animation, in which it can exist long time. Thus, Escherichia remains viable at -190 0 C for up to 4 months, the causative agent of listeriosis at -10 0 C for up to 3 years. Low temperatures stop putrefactive and fermentation processes. The preservation of food in refrigerators is based on this principle.
High temperature has a detrimental effect on microbes. The higher the temperature, the less time is required to inactivate microorganisms. The bactericidal effect of high temperatures is based on the destruction of enzymes due to protein denaturation and disruption of the osmotic barrier.
Different types of microorganisms have different resistance to high temperatures; the resistance of spores and vegetative cells differs significantly. Thus, most vegetative forms of pathogenic microorganisms die at a temperature of 80...100 0 C for 1 minute, and spores of the anthrax pathogen can withstand boiling for more than 1 hour.
Effect of visible radiation (light) .
Visible (scattered light), having a wavelength of 300...1000 nm, has the ability to inhibit the growth and vital activity of most microorganisms. In this regard, the cultivation of microorganisms is carried out in the dark. Visible light only has a positive effect on bacteria that use light for photosynthesis.
Direct sunlight has a more active effect on microorganisms than diffuse light. The bactericidal effect of light is associated with the formation of hydroxyl radicals and other highly reactive substances that destroy substances that make up the cell. For example, enzyme inactivation occurs.
Saprophytic microorganisms are more resistant to light than pathogenic ones. This is explained by the fact that, being more often exposed to direct sunlight, they are more adapted to it. In this regard, it should be noted the great hygienic role of sunlight. It is under the influence of solar radiation that the air self-purifies, upper layers soil and water.
Ultraviolet radiation .
Ultraviolet radiation with a wavelength of 295...200 nm is bactericidal, that is, capable of having a detrimental effect on microorganisms. The mechanism of action of ultraviolet radiation is its ability to partially or completely suppress DNA replication and damage ribonucleic acids (especially mRNA).
Ultraviolet radiation is widely used for air sanitation in livestock buildings, laboratories, industrial workshops, and microbiological boxes. The industry produces various lamps for air disinfection. In livestock farming practice, IKUF-1 installations are widely used as a source of ultraviolet and infrared radiation.
Ionizing radiation .
Ionizing (X-ray) radiation is electromagnetic radiation with a wavelength of 0.006...10 nm. Depending on the wavelength, gamma radiation, beta radiation and alpha radiation are distinguished. Gamma radiation has the most active effect on biological objects, but even its bactericidal properties are significantly lower than the bactericidal properties of ultraviolet radiation. The death of bacteria occurs only when they are irradiated with large doses from 45,000 to 280,000 roentgens. Some species are able to survive in water nuclear reactors, where the amount of radioactive exposure reaches 2...3 million roentgens. Moreover, evidence has been obtained that the impact of small doses of gamma radiation on pathogenic microorganisms can enhance their virulent properties.
The mechanism of action of X-ray radiation is damage to nuclear structures, in particular nucleic acids of the cytoplasm, which leads to the death of a microbial cell or a change in its genetic properties (mutation).
Electricity.
Low and high frequency electric current destroys microorganisms. Ultra-high frequency currents have a particularly strong bactericidal effect. They vibrate the molecules of all elements of the cell, resulting in rapid and uniform heating of the entire mass of the cell, regardless of the ambient temperature. In addition, it was found that prolonged exposure to high frequency currents leads to electrophoresis of some components of the nutrient medium. The resulting compounds inactivate the microbial cell.
Ultrasound.
The mechanism of the bactericidal effect of ultrasound (waves with a frequency of 20,000 Hz) is that a cavitation cavity is formed in the cytoplasm of microorganisms in a liquid medium, which is filled with liquid vapor; pressure arises in the bubble, which leads to the disintegration of cytoplasmic structures. Ultrasound is used to sterilize food and disinfect objects.
Aeroionization.
Aeroions carrying a positive or negative charge appear in the air during artificial or natural ionization. Negatively charged ions have the greatest effect on bacteria, acting already in medium concentrations (5 * 10 4 in 1 cm 3 of air). Positively charged ions have a less pronounced bactericidal effect; they are able to inhibit the growth and development of microorganisms only in high concentrations (10 6 in 1 cm 3 of air). The strength of air ions depends on their concentration, duration of exposure and distance from the source. Air ions are used to disinfect the air of residential premises, workshops of enterprises, and medical institutions.
Almost all factors of physical influence on microorganisms can be used for the purpose of sterilization. Sterilization is the destruction of pathogenic and non-pathogenic microorganisms, their vegetative and spore forms in any object. Nutrient media, glassware, instruments, dressings, and gowns are subjected to sterilization. Air and objects in microbiological boxes are also sterilized.
The mechanism of action of various sterilization methods is not the same, but each is based on the ability to disrupt the life processes of a microbial cell (denaturation of proteins, inhibition of the function of enzyme systems).
Physical sterilization methods:
1. Calcination (flambéing). Metal objects are exposed (loops, needles, scalpel, scissors, spatula).
2. Sterilization by boiling. Needles, syringes, tweezers, scissors, scalpels and other instruments that are placed in sterilizers on lattice inserts are sterilized by boiling. Distilled water is poured into the sterilizer in an amount sufficient to completely cover the instruments. You can add 2% sodium bicarbonate to the water. Boil for 25 - 30 minutes.
3. Dry heat sterilization. Sterilization is carried out using dry heated air in a double-walled drying cabinet (Pasteur oven). The outside of the cabinet is lined with heat-proof material. Temperature control is carried out using a temperature sensor. Clean, pre-dried glassware wrapped in parchment paper is sterilized in an oven. Sterilization modes: 155…160 0–2 hours; 165…170 0 – 1…1.5 hours; 180 0 – 1 hour. The exposure time is noted from the moment the temperature reaches the set value.
4. Sterilization with flowing steam. Sterilization is carried out in a Koch apparatus, which is a vessel with a loosely closed lid. At the bottom of the apparatus there is a lattice stand, to the level of which water is poured. A vessel with a lattice bottom containing objects to be sterilized (nutrient media) is placed on the stand. As water boils, vapors are formed that heat the contents of the vessel. Sterilization time is 30...40 minutes. A single sterilization destroys only vegetative forms of bacteria, and the spores retain their viability; sterilization is carried out “fractionally” - for three days in a row. In this way, media with carbohydrates, milk, media with gelatin are sterilized, that is, substrates that cannot withstand heating above 100 0 C, prolonged exposure to steam or dry heat.
5. Tyndalization– this is fractional sterilization in a water bath at 56...58 0 C for 5...6 days: on the first day they are heated for 2 hours, on subsequent days - for 1 hour. The method is used to sterilize materials that degrade at temperatures above 58...60 0 C - substances containing proteins (blood serum).
6. Pasteurizationis a method of incomplete sterilization used to preserve the nutritional value of a food product, which may be reduced by boiling. The product is heated at 80 0 C for 30 minutes, and then sharply cooled to 4...8 0 C. Sharp cooling prevents the germination of spores and the subsequent proliferation of bacteria.
7. Steam sterilization under pressure (autoclaving). This is the most effective method sterilization. The principle of sterilization is based on the fact that pure saturated water vapor at high pressure, condensing, increases the temperature inside the autoclave above the boiling point. As the steam pressure increases, the temperature in the sterilization chamber increases accordingly: 50.6 kPa (0.5 atm.) – 110...112 0 C, 101.3 kPa (1 atm.) – 120...121 0 C, 151.9 kPa (1.5 atm.) – 124…126 0 C, 202.6 kPa (2 atm.) – 132…133 0 C. The designs and volume of the sterilization chamber of autoclaves may be different (horizontal and vertical), but the principle of operation remains the same same. In an autoclave, nutrient media that can withstand temperatures above 100 0 C, glassware wrapped in paper, dressings, and gowns (in bags) are sterilized. In addition, microbial cultures, spent nutrient media, and dishes are disinfected. The operating modes of the autoclave require constant monitoring. For this purpose, chemical and biological methods are used.
8. Sterilization by filtration . The material is passed through bacteriological filters. Filtration is associated with the mechanical retention of bacteria by fine-pored filters and with the adsorption capacity of the material from which the filter is made. Liquids that cannot withstand heat are usually subjected to filtration. There are filters:
· ceramic - they are made from kaolin or quartz sand;
· asbestos - Seitz filters (plates made from a mixture of asbestos and cellulose);
· membrane - they look like thin sheets of white paper, they are made from hemicellulose, treated with appropriate reagents, temperature and pressing. These filters are distinguished by diameter and pore size and have the most accurate calibration.
The sterility of the filtrates is controlled by seeding on thermostatically controlled nutrient media.
9. Sterilization by ultraviolet radiation. In the laboratory, the source of ultraviolet radiation is usually bactericidal lamps used for air disinfection.
Ultrasound sterilization. Ultrasound is used to sterilize water, milk, some products, and leather raw materials. The sterilizing effect of ultrasound is associated with the destruction of the bacterial cell under the influence of cavitation cavities that arise in the cytoplasm.Introduction……………………………………………………………..………….….2
1) The influence of physical factors on microorganisms…………………..………3
1.1Radiations……………………………………………………..………………………3
1.2Ultrasound…………………………………….....………………………4
2) Ionizing radiation…………………………..…….…………………….5
2.1 Practical use of ionizing radiation………......7
3) Conclusion………………………………………………………...……..………8
References………………….……………………………..………….9
Introduction
All existing microorganisms live in continuous interaction with the external environment in which they are located, and therefore are exposed to various influences. In some cases they can promote better development, in others they can suppress their vital functions. It must be remembered that variability and rapid change of generations allows one to adapt to different living conditions. Therefore, new signs are quickly established.
Being in the process of development in close interaction with the environment, microorganisms can not only change under its influence, but can change the environment in accordance with their characteristics. So, during the process of respiration, microbes release metabolic products, which in turn change the chemical composition of the environment, therefore the reaction of the environment and the content of various chemicals change.
All factors influencing the development of microbes are divided into:
· Physical
· Chemical
· Biological
Below we will take a closer look at each of the factors.
1) The influence of physical factors on microorganismsTemperature in relation to temperature conditions, microorganisms are divided into thermophilic, psychrophilic and mesophilic.
· Thermophilic species . The optimal growth zone is 50-60°C, the upper growth inhibition zone is 75°C. Thermophiles live in hot springs and participate in the processes of self-heating of manure, grain, and hay.
· Psychrophilic species (cold-loving) grow in the temperature range of 0-10°C, the maximum growth inhibition zone is 20-30°C. These include most saprophytes that live in soil, fresh and sea water. But there are some species, for example, Yersinia, psychrophilic variants of Klebsiella, pseudomonads, that cause diseases in humans.
· Mesophilic species grow best within 20-40°C; maximum 43-45°C, minimum 15-20°C. They can survive in the environment, but usually do not reproduce. These include most pathogenic and opportunistic microorganisms.
1.1 Radiation
Sunlight has a detrimental effect on microorganisms, with the exception of phototrophic species. Short-wave UV rays have the greatest microbicidal effect. Radiation energy is used for disinfection, as well as for sterilization of thermolabile materials.
Ultra-violet rays(primarily short-wavelength, i.e. with a wavelength of 250-270 nm) act on nucleic acids. The microbicidal effect is based on the rupture of hydrogen bonds and the formation of thymidine dimers in the DNA molecule, leading to the appearance of non-viable mutants. The use of ultraviolet radiation for sterilization is limited by its low permeability and high absorption activity of water and glass.
X-ray And g-radiation V large doses also causes the death of microbes. Irradiation causes the formation of free radicals that destroy nucleic acids and proteins, followed by the death of microbial cells. Used for sterilization of bacteriological preparations and plastic products.
Microwave radiation used for rapid re-sterilization of long-term stored media. The sterilizing effect is achieved by quickly raising the temperature.
1.2Ultrasound.
Certain frequencies of ultrasound, when exposed artificially, can cause depolymerization of the organelles of microbial cells; under the influence of ultrasound, gases located in the liquid medium of the cytoplasm are activated and high pressure arises inside the cell (up to 10,000 atm). This leads to rupture of the cell membrane and cell death. Ultrasound is used to sterilize food products (milk, fruit juices) and drinking water.
Pressure.
Bacteria are relatively little sensitive to changes in hydrostatic pressure. Increasing the pressure to a certain limit does not affect the growth rate of ordinary terrestrial bacteria, but eventually begins to interfere with normal growth and division. Some types of bacteria can withstand pressures of up to 3,000 - 5,000 atm, and
bacterial spores - even 20,000 atm.
In conditions of deep vacuum, the substrate dries out and life is impossible.
Filtration.
To remove microorganisms, various materials are used (fine-porous glass, cellulose, koalin); they provide effective elimination of microorganisms from liquids and gases. Filtration is used to sterilize temperature-sensitive liquids, separate microbes and their metabolites (exotoxins, enzymes), and also to isolate viruses.
2) Ionizing radiation
Streams of photons or particles, the interaction of which with a medium leads to the ionization of its atoms or molecules. There are photon (electromagnetic) and corpuscular
Toward photonic I.I. include vacuum UV and characteristic X-rays, as well as radiation arising from radioactive decay and other nuclear reactions (mainly g-radiation) and when charged particles are decelerated into an electric or magnetic field - bremsstrahlung X-rays, synchrotron radiation.
To corpuscular I.I. include fluxes of a- and b-particles, accelerated ions and electrons, neutrons, fission fragments of heavy nuclei, etc.
Mechanisms of action of ionizing radiation on living organisms
The processes of interaction of ionizing radiation with matter in living organisms lead to a specific biological effect, resulting in damage to the body. In the process of this damaging action, three stages can be roughly distinguished:
b. the effect of radiation on cells;
c. the effect of radiation on the whole organism.
The primary act of this action is the excitation and ionization of molecules, as a result of which free radicals arise (direct action of radiation) or the chemical transformation (radiolysis) of water begins, the products of which (OH radical, hydrogen peroxide - H 2 O 2, etc.) enter into chemical reaction with molecules of a biological system.
Primary ionization processes do not cause major disturbances in living tissues. The damaging effect of radiation is apparently associated with secondary reactions in which bonds within complex organic molecules are broken, for example SH groups in proteins, chromophore groups of nitrogenous bases in DNA, unsaturated bonds in lipids, etc.
The effect of ionizing radiation on cells is due to the interaction of free radicals with molecules of proteins, nucleic acids and lipids, when, as a result of all these processes, organic peroxides are formed and transient oxidation reactions occur. As a result of peroxidation, many altered molecules accumulate, as a result of which the initial radiation effect is greatly enhanced. All this is reflected primarily in the structure of biological membranes, their sorption properties change and permeability increases (including membranes of lysosomes and mitochondria). Changes in lysosome membranes lead to the release and activation of DNase, RNase, cathepsins, phosphatase, mucopolysaccharide hydrolysis enzymes and a number of other enzymes.
The released hydrolytic enzymes can, by simple diffusion, reach any cell organelle into which they easily penetrate due to increased membrane permeability. Under the influence of these enzymes, further decomposition of the macromolecular components of the cell occurs, including nucleic acids and proteins. Uncoupling of oxidative phosphorylation as a result of the release of a number of enzymes from mitochondria, in turn, leads to inhibition ATP synthesis, and hence to disruption of protein biosynthesis.
Thus, the basis of radiation damage to cells is a violation of the ultrastructures of cellular organelles and associated metabolic changes. In addition, ionizing radiation causes the formation in the tissues of the body of a whole complex of toxic products that enhance the radiation effect - the so-called radiotoxins. Among them, the most active are lipid oxidation products - peroxides, epoxides, aldehydes and ketones. Formed immediately after irradiation, lipid radiotoxins stimulate the formation of other biologically active substances - quinones, choline, histamine and cause increased breakdown of proteins. When administered to non-irradiated animals, lipid radiotoxins have effects reminiscent of radiation injury. Ionizing radiation has the greatest effect on the cell nucleus, inhibiting mitotic activity.