Anaerobes and aerobes are two forms of existence of organisms on earth. This article is about microorganisms.
Anaerobes are microorganisms that develop and multiply in an environment that does not contain free oxygen. Anaerobic microorganisms are found in almost all human tissues from pyoinflammatory foci. They are classified as conditionally pathogenic (they exist in humans in the nome and develop only in people with a weakened immune system), but sometimes they can be pathogenic (pathogenic).
There are facultative and obligate anaerobes. Facultative anaerobes can develop and multiply both in oxygen-free and oxygen environments. These are microorganisms such as E. coli, Yersinia, staphylococcus, streptococcus, shigella and other bacteria. Obligate anaerobes can only exist in an anoxic environment and die when free oxygen appears in the environment. Obligate anaerobes are divided into two groups:
- spore-forming bacteria, otherwise known as clostridia
- bacteria that do not form spores, or otherwise non-clostridial anaerobes.
Clostridium is the causative agent of anaerobic clostridial infections - botulism, clostridial wound infections, tetanus. Non-clostridial anaerobes are the normal microflora of humans and animals. These include rod-shaped and spherical bacteria: bacteroids, fusobacteria, peillonella, peptococci, peptostreptococci, propionibacteria, eubacteria and others.
But non-clostridial anaerobes can significantly contribute to the development of purulent-inflammatory processes (peritonitis, abscesses of the lungs and brain, pneumonia, pleural empyema, phlegmon of the maxillofacial region, sepsis, otitis, and others). Most anaerobic infections caused by non-clostridial anaerobes are endogenous (of internal origin, caused by internal causes) and develop mainly with a decrease in the body's resistance, resistance to pathogens as a result of injuries, operations, hypothermia, and reduced immunity.
The main part of the anaerobes that play a role in the development of infections are bacteroids, fusobacteria, peptostreptococci and spore bacilli. Half of purulent-inflammatory anaerobic infections are caused by bacteroids.
- Bacteroides-rods, 1-15 microns in size, non-motile or moving with the help of flagella. They secrete toxins that act as virulence factors (pathogens).
- Fusobacteria are rod-shaped obligate (surviving only in the absence of oxygen) anaerobic bacteria that live on the mucous membrane of the mouth and intestines, can be immobile or mobile, contain a strong endotoxin.
- Peptostreptococci are spherical bacteria, arranged in twos, fours, irregular clusters or chains. These are non-flagellated bacteria that do not form spores. Peptococci is a genus of spherical bacteria represented by a single species P.niger. Arranged singly, in pairs or in clusters. Peptococci do not have flagella and do not form spores.
- Veionella is a genus of diplococci (bacteria of a coccal form, the cells of which are arranged in pairs), arranged in short chains, immobile, do not form spores.
- Other non-clostridial anaerobic bacteria that are isolated from infectious foci of patients are propionic bacteria, volinella, the role of which is less studied.
Clostridium is a genus of spore-forming anaerobic bacteria. Clostridia live on the mucous membranes of the gastrointestinal tract. Clostridia are mainly pathogenic (disease-causing) for humans. They secrete highly active toxins specific to each species. The causative agent of anaerobic infection can be either one type of bacteria or several types of microorganisms: anaerobic-anaerobic (bacteroids and fusobacteria), anaerobic-aerobic (bacteroids and staphylococci, clostridia and staphylococci)
Aerobes are organisms that need free oxygen for life and reproduction. Unlike anaerobes, aerobes take part in the process of generating the energy they need. Aerobes include animals, plants and a significant part of microorganisms, among which they are isolated.
- obligate aerobes - these are "strict" or "unconditional" aerobes, they receive energy only from oxidative reactions involving oxygen; these include, for example, some species of Pseudomonas, many saprophytes, fungi, Diplococcus pneumoniae, diphtheria bacilli
- in the group of obligate aerobes, microaerophiles can be distinguished - for their vital activity they need a low oxygen content. When released into the normal environment, such microorganisms are suppressed or killed, since oxygen adversely affects the action of their enzymes. These include, for example, meningococci, streptococci, gonococci.
- facultative aerobes - microorganisms that can develop in the absence of oxygen, for example, a yeast bacillus. Most pathogenic microbes belong to this group.
Each aerobic microorganism has its own minimum, optimum and maximum oxygen concentration in its environment, which is necessary for its normal development. Increasing the oxygen content beyond the “maximum” boundary leads to the death of microbes. All microorganisms die at an oxygen concentration of 40-50%.
Obligate anaerobes are obviously an example of early anaerobic life forms. This is consistent with the theory of the origin of life on Earth, according to which the primary organisms of our planet were anaerobes. A comparative biochemical analysis leads to the conclusion that the energy metabolism of all organisms without exception is based on the same strikingly similar chains of reactions that are not associated with the consumption of free oxygen - reactions that occur in the cells of modern anaerobes (according to A.I. Oparin).[ ...]
An obligate organism (from Latin - obligatory) is an organism strictly specialized to a certain type of nutrition, respiration, environmental factors (monophages, necrophages, aerobes, anaerobes, etc.).[ ...]
Anaerobe - an organism that can live in an oxygen-free environment. There are obligate anaerobes - permanently living in an oxygen-free environment and facultative - capable of living both without oxygen and in its presence (organisms of city sewers, primary sedimentation tanks, etc.).[ ...]
Obligate anaerobes - organisms that are unable to live in an oxygen environment (some bacteria).[ ...]
Obligate anaerobes include the genera Desulfovibrio, Desuljotomaculum, some species of the genus Bacillus. Bacilli are found among various ecological groups of microorganisms and adapt to any oxygen regime.[ ...]
In obligate aerobes and facultative anaerobes, in the presence of oxygen, catabolism proceeds in three stages: preparatory, oxygen-free, and oxygen. As a result, organic substances break down into inorganic compounds. In obligate anaerobes and facultative anaerobes, with a lack of oxygen, catabolism proceeds in the first two stages: preparatory and anoxic. As a result, intermediate organic compounds are formed that are still rich in energy.[ ...]
Spores of obligate mesophilic and thermophilic anaerobes - causative agents of bombing - in canned food before sterilization are determined: after registering an increased contamination of the product before sterilization - immediately, after registering a bacteriological defect, if the production of this type of canned food continues - immediately, preventive control, at least 1-2 times a week for each type of canned food from each line.[ ...]
The cytoplasm of anaerobes has a composition and structure similar to that of aerobes. The cytoplasm of some anaerobes contains inclusions of the reserve nutrient granulosa, a starch-like polysaccharide. On ultrathin sections, this substance can be seen in the form of light spherical inclusions (Fig. 45). Lipid bodies (drops of poly-p-hydroxybutyric acid) are rare in the cytoplasm of obligate anaerobes.[ ...]
These bacteria are also very sensitive to oxygen. Thus, the differences between obligate anaerobes and aerobes relate primarily to the enzymatic provision of terminal oxidation. In anaerobes, free oxygen cannot be used as the final hydrogen acceptor.[ ...]
Butyric acid bacteria are obligate anaerobes, that is, strict anaerobes. They are extremely widespread in nature: up to 90% of soil samples, as a rule, contain representatives of this group of bacteria.[ ...]
Green bacteria are strict anaerobes and obligate phototrophs. An exception are representatives of the genus Chloroflexis. They grow only under aerobic conditions, both in light and in the dark. However, even phototrophic bacteria that grow well in the dark develop better in the presence of light. Depending on the organism, the optimal lighting conditions for its growth may be different. Some species grow well in low light (100-300 lux), others in stronger light (700-2000 lux).[ ...]
A significant number of bacteria - obligate aerobes and facultative anaerobes - are able to exist due to the use of water pollution (impurities) as a source of nutrition. At the same time, part of the used organic substances is spent on energy needs, and the other part is spent on the synthesis of the cell body. Part of the substance consumed for energy needs is completely oxidized by the cell, i.e., to CO2, H2O, >N3. Oxidation products - the metabolite - are excreted from the cell into the external environment. The reactions of synthesis of cellular substance also take place with the participation of oxygen. The amount of oxygen required by microorganisms for the entire cycle of the reaction of synthesis and energy production is BOD.[ ...]
In addition to glycolysis, facultative anaerobes have other ways of anaerobic ATP generation associated with the decarboxylation of α-ketoglutaric and pyruvic acids, the elimination of their carboxyl groups, and the formation of CO2. This complex, multi-step chain of reactions has not yet been studied enough. But from all that has been said, it follows that the set of enzymes in the tissues of facultative anaerobes should, if not qualitatively, then at least quantitatively and in terms of the nature of activity regulation, differ significantly from what takes place in obligate aerobes, and allow them to draw energy from aerobic, and from anaerobic oxidative processes.[ ...]
When studying the effect of oxygen on the development of obligate anaerobes, it was shown that oxygen does not have a detrimental effect on anaerobes if the ORP of the environment is low. Indeed, if reducing agents that reduce ORP are added to the medium, then some anaerobic microorganisms are able to grow on such media under aerobic conditions. In general, anaerobes can be attributed to such microorganisms, the growth and development of which is confined to natural substrates that are deprived of free oxygen and have a low redox potential.[ ...]
According to Campbell and Postgate, all spore-forming anaerobes with a constant ability to reduce sulfates were isolated in a new genus - BeviHo-1; It includes obligate anaerobes with gram-negative, straight or curved rods that swell in thermophilic forms. Spores are formed terminally or subterminally. The composition of DNA ranges from 41.7-49.2 mol.% G + C.[ ...]
Most purple sulfur bacteria are strict anaerobes and obligate phototrophs, i.e., their growth is possible only under illumination. Only three species are known to grow in the presence of air, and not only in the light, but also in the dark, albeit slowly. These are A. roseus, E. shaposhnikovii and T. roseopersicina. All non-sulfur purple bacteria also grow under anaerobic conditions, but are mostly facultative aerobes. Until recently, it was believed that the growth of purple bacteria in the dark is possible only under aerobic or microaerophilic conditions, since in the absence of light they receive energy in the process of respiration. However, it has recently been established that R. rubrum and a number of representatives of Rhodopseudomonas grow in the dark and under strictly anaerobic conditions due to the fermentation of certain organic substrates. The purple sulfur bacteria E. shaposhnikovii and T. roseopersicina seem to have the same possibility.[ ...]
So, despite the fact that anaerobic saprophages, both obligate and facultative, make up a smaller part of the community components, they nevertheless play an important role in the ecosystem, since only they are capable of respiration in the oxygen-free lower tiers of the system deprived of light. By occupying these inhospitable habitats, they "save" energy and materials, making them available to most aerobes. Thus, what seems to be an "inefficient" way of breathing turns out to be an integral part of the "efficient" exploitation of energy and material resources by the ecosystem as a whole. For example, the efficiency of wastewater treatment, which is provided by a human-managed heterotrophic ecosystem, depends on the consistency between the activities of anaerobic and aerobic saprophages.[ ...]
The toxic effect of air oxygen on the growth and development of obligate anaerobes and the attraction to a low redox potential, according to modern concepts, can be explained by the fact that molecular oxygen and high ORP can cause irreversible oxidation of vital enzymes that determine the main processes of their metabolism. [ . ..]
Methanobacterium omelianskii, Bad. formicicum, Methanosarcina barkeri are obligate anaerobes and are relatively difficult to isolate. Culture Bad. formicicum decomposes formic acid with the formation of various decomposition products, and the direction of the process depends on the redox potential of the medium. Under conditions of relative anaerobiosis, as established by JI. V. Omelyansky j formic acid decomposes with the formation of hydrogen and carbon dioxide; at the same time, the potential of the nutrient medium decreases to hH2 12-12.9 and anaerobic conditions are created. Upon decomposition under anaerobic conditions and a decrease in rH2 to 6-7, formic acid decomposes with the formation of methane; in the range of values hH2 16-22, the decomposition of formic acid occurs only with the formation of carbon dioxide.[ ...]
This chapter talks about spore-forming anaerobic bacteria, and only about obligate, i.e., those organisms that are not able to develop under aerobic conditions, in contrast to facultative ones, capable of living both due to respiration, using molecular oxygen, and due to " nitrate respiration" or fermentation of various organic substances under anaerobic conditions. It should be noted that anaerobic spore-bearing bacteria are less studied than aerobic ones, due to the significant difficulties that researchers encounter in isolating and cultivating anaerobes.[ ...]
Genus Peptococcus. Cells solitary, in pairs, tetrads, aggregates. Obligate anaerobes with proteolytic activity and fermenting various organic compounds. The optimum temperature is 37 °C. The type species is Peptococcus niger, which produces a black pigment. They live in feces, dirt, in the human body and are capable of causing septic infections under certain conditions.[ ...]
Anaerobiosis is also characteristic of facultative anaerobic microorganisms. Unlike the latter, obligate anaerobes cannot develop in the presence of oxygen; moreover, oxygen in molecular form is poisonous to anaerobes.[ ...]
The results of six studies, in which nine different types of obligate and facultative anaerobes were used under anaerobic conditions, growing on seven different substrates, gave an average value of UCcal = 0.130 g/kcal.[ ...]
Microorganisms belonging to different taxonomic groups can oxidize molecular hydrogen. Among them there are strict anaerobes, facultative anaerobes and obligate aerobes. Facultative anaerobes and aerobes with this property include Escherichia coli, Paracoccus denitrificans, Streptococcus faecalis and some representatives: Bacillus, Pseudomonas, Alcaligenes, Acetobacter, Azotobacter, Mycobacterium, Nocardia, Proteus, as well as certain types of blue-green and green algae.[ ...]
If we agree with the statement (quite convincingly substantiated by the data of comparative physiology and biochemistry) that obligate anaerobes are an example of early forms of life on Earth, then the question arises whether the origin and evolution of anaerobes were reflected in the composition and structure of their DNA - the keeper of genetic information . It is now well known that deoxyribonucleic acids of the entire organic world have a single structural plan, and on the other hand, there are unlimited possibilities for variations in the composition and structure of these compounds. It is quite logical to think that the emergence of DNA in the history of life on Earth was a very important and, probably, even a decisive factor in the differentiation and isolation of new groups and species of living beings. Since it is nucleic acids that are directly related to heredity and variability, they must be the material basis of the evolutionary process.[ ...]
These results allow us to conclude that the leading role in the processes of anaerobic decomposition of organic material is played by obligate anaerobic bacteria. However, the systematic detection of aerobes and facultative anaerobes in the contents of digesters indicates that these microorganisms are also involved in the destruction of organic substances, and under certain conditions their number can increase significantly. Thus, when glucose is added to the fermented liquid, the number of aerobic and facultative anaerobic bacteria increases from 1 X 10b to 3.2 X 109 cells / ml (quoted from ).[ ...]
When the treatment plant is overloaded with organic pollution, when the amount of incoming air is not enough, obligate (unconditional) or facultative anaerobes develop, for which oxygen is harmful.[ ...]
In the second phase of alkaline or methane fermentation, methane and carbonic acid are formed from the end products of the first phase as a result of the vital activity of methane-forming bacteria - non-spore-bearing obligate anaerobes, very sensitive to environmental conditions. The studied species of methane-forming bacteria belong to three genera: Methanobacterium, Methanococcus, Methanosarcina.[ ...]
Some anaerobic microorganisms use bound oxygen, which is part of compounds such as sulfates or nitrates, as an acceptor. In the presence of oxygen, they have aerobic respiration, and in oxygen-free environments they use the oxygen of nitrates as an acceptor, reducing them to nitrogen or its lower oxides. Bacteria that reduce sulfates to hydrogen sulfide in the process of respiration are obligate anaerobes, for example, VeviNowsh-gyu (keiUipcans.[ ...]
Different species and genera of bacteria are not equally related to adaptation. Some adapt faster to changing conditions, others slower. Bacteria of the genus Rseuiotopaz adapt better than others.[ ...]
But animals are known that can live equally normally both with a good availability of oxygen, and with an extremely low content of it, and with an almost complete absence, and even those that not only do not need oxygen, but are even harmful. The former are called facultative anaerobes, the latter are obligate. The former include aquatic turtles and many fish that lead a benthic lifestyle. The fact is that in the bottom water the oxygen content can reach up to 15% of the value that is observed when the water is saturated with air.[ ...]
The use of electron microscopy methods, which make it possible to study the distribution of dehydrogenases in whole cells, shows that dehydrogenases in anaerobic spore-bearing bacteria are obviously also associated with membranes, which play a huge role in living organisms, especially in the processes of energy metabolism. At the same time, in other anaerobes, the reduction of electron acceptors is also observed in the cytoplasm. Perhaps these phenomena are associated with a different set of enzymes in different species or with nonspecific reduction of dyes in the cytoplasm.[ ...]
The depletion of molecular oxygen in situ leads to a slowdown in heat release, and the supply of oxygen due to convection also decreases accordingly. At the same time, the accumulation of carbon dioxide during the composting stage creates microaerophilic conditions, which lead to an increase in the number of first facultative and then obligate anaerobes. In contrast to aerobic metabolism, in which the mineralization of waste is often achieved with the help of one type of bacteria, anaerobic biodegradation requires the joint metabolism of microorganisms of different species that are part of a mixed population. This population of microorganisms interacting with each other is able to use various inorganic electron acceptors, often in a sequence corresponding to the release of energy during this reaction. Since most bacteria require certain electron acceptors, this sequence leads to significant changes in the composition of the microbial population. Species that are able to use more oxidized acceptors gain thermodynamic and therefore kinetic advantages.[ ...]
Thus, the conversion of organic matter in methanetanks occurs in two stages: fermentation of the substrate to fatty acids (non-methanogenic) and formation of CH4 and CO2 from fatty acids (methanogenic). During the first stage, the main role is played by anaerobic bacteria of the genera Clostridium, Bacteroides, etc. The second stage is carried out by a unique group of obligate anaerobes - methane bacteria of the genera Methano-bacterium, Methanobacillus, Methanococcus, Methanosarcina.[ ...]
The presence of acids in the medium causes its acidic reaction. In addition to SFA, the products of the decomposition of the first phase are lower fatty alcohols, amino acids, some aldehydes and ketones, glycerin, as well as carbon dioxide, hydrogen, hydrogen sulfide, ammonia and some other compounds. This phase of the process is carried out by bacteria belonging to facultative anaerobes (lactic acid bacteria, acetic acid, propionic acid, etc.) and obligate anaerobes (butyric acid bacteria, cellulose, acetonobutyl, etc.).[ ...]
Fermentation goes through the stages of formation of pyruvic acid with its subsequent transformation. The source of nitrogen for butyric bacteria are peptones, amino acids and ammonium salts, some of the bacteria also use free nitrogen. Carbohydrates serve as a source of energy and carbon for them. The causative agents of butyric fermentation are obligate anaerobes. These are large, mobile spore-forming rods 3-10 microns long and 0.5-1.5 microns in diameter. The optimum temperature for their development is 35-37°C, pH limit values are 6-8.[ ...]
Photosynthetic bacteria are mainly aquatic (marine and freshwater) organisms; in most cases they play an insignificant role in the production of organic matter. But they are able to function in conditions that are generally unfavorable for most green plants, and in water sediments they participate in the cycle of some elements. For example, green and purple sulfur bacteria play an important role in the sulfur cycle (see Figure 4.5). These obligate anaerobes (capable of life only in the absence of oxygen) are found in the boundary layer between the oxidized and reduced zones in sediments or water, where light hardly penetrates. These bacteria can be observed in littoral silt, where they often form distinct pink or purple layers directly below the upper green layers of mud-dwelling algae (in other words, at the uppermost limit of the anaerobic, or reduced, zone, where there is light but little oxygen) . In a study of Japanese lakes (Takahashi and Ichimura, 1968), it was calculated that the share of photosynthetic sulfur bacteria in most lakes accounts for only 3-5% of the total annual production of photosynthesis, but in stagnant lakes rich in H2S, this share rises to 25%. Non-sulfur photosynthetic bacteria, on the contrary, are usually facultative aerobes (able to function both in the presence and in the absence of oxygen). In the absence of light, they, like many algae, can behave as heterotrophs. Thus, bacterial photosynthesis can be useful in polluted and eutrophic waters, in connection with which its study is now intensifying, but it cannot replace the "real" photosynthesis with the release of oxygen, on which all life on Earth depends.[ ...]
Free-living diazotrophs are most vulnerable to erosion of arable land. At the first stages of degradation, the mechanisms of anaerobic nitrogen fixation are rapidly suppressed due to a decrease in the amount of the labile part of organic matter (Khaziev, 1982; Khaziev and Bagautdinov, 1987). The pool of diazotrophs is extremely sensitive to the carbon substrate. Obligate anaerobes of the genus Clostridium, in contrast to aerobic forms functioning on a wide range of C compounds, including humic and fulvic acids, use a narrow carbohydrate flow (Klevenskaya, 1974; Mishustin and Emtsev, 1974). The diverse composition of the carbohydrate fund of the soils of the chernozem series of Western Siberia (Klevenskaya, 1991) provides a sufficient energy and trophic level of clostridia, contributing to their certain predominance in soils unaffected by erosion. The transformation of the microbial community intensifies with the development of erosion on the slope of the southern exposure, where, as is known, in comparison with the northern counterparts, the thickness of the humus horizon is less, the processes of mineralization of organic matter and nitrogen are more intense (Chuyan, Chuyan, 1993).[ ...]
The formation of the microflora of the digester occurs due to microorganisms that have fallen along with sewage or sediment. In terms of species composition, the biocenosis of digesters is much poorer than aerobic biocenoses, of which only about 50 species of bacteria have been isolated that are capable of carrying out the first stage of pollution splitting - the stage of acid formation. Along with obligate anaerobes, facultative anaerobes can also be found in the digester. The total number of bacteria in the sediment ranges from 1 to 15 mg/ml. The end product of the fermentation process of this group of microorganisms are lower fatty acids, carbon dioxide, ammonium ions, hydrogen sulfide.[ ...]
FEEDING AREA (waters) - region. inflow of precipitation, surface or groundwater into the aquifer (ST SEV 2086-80). UNLOADING AREA (water) - region. groundwater outlets to the surface of the earth, into reservoirs or watercourses, as well as their overflow into adjacent aquifers (ST SEV 2086-80). See Unloading. Afforestation - restoration or creation of forest areas by sowing seeds of woody plants, planting their seedlings or promoting natural reforestation (eg, in the development of dumps). See reforestation. OBLIGATORY ORGANISM [from lat. obligatory] - an organism strictly specialized for a certain type of nutrition, respiration, environment (monophages, anaerobes, etc.).[ ...]
These microbes got their name for their ability to rapid oscillatory movements (from the Latin "vibrare" - to oscillate). Vibrios are shaped like short, comma-shaped sticks. After division, they often remain linked ends, forming spirals. They are unable to break down fiber. Many use phenols and other cyclic compounds. The length of individual vibrios rarely exceeds 10 microns, and their diameter is from 1 to 1.5 microns. Some of them are strict anaerobes, others are obligate aerobes or facultative anaerobes (growing in the presence of oxygen and at a reduced concentration of it). These are mainly saprophytes, widespread in polluted rivers and lakes of our planet.[ ...]
During biological oxidation, redox reactions occur, accompanied by the removal of hydrogen atoms from some compounds (donors) and its transfer to others (acceptors), or reactions associated with the transfer of electrons from a donor to an acceptor. These processes are carried out with the participation of enzymes belonging to the class of oxidoreductases. Respiration processes in which molecular oxygen is an acceptor of hydrogen or electrons are called aerobic. If the acceptors are other inorganic or organic compounds, then this type of respiration is called anaerobic. According to the type of respiration, two groups of microorganisms are distinguished: aerobes (oxybiotic forms), which require oxygen for respiration, and anaerobes (anoxibiotic forms), which develop in the absence of oxygen. There is no sharp difference between them. Along with strict (obligate) aerobes and anaerobes, there are microorganisms that can live in the presence of oxygen and without it. These are microaerophiles, the optimum oxygen content in the air for which is 0.5-1%, and facultative anaerobes. So, Escherichia coli is a facultative anaerobe.
A., dying in the presence of free oxygen in the environment ... Big Medical Dictionary
See Anaerobic Organisms. Geological dictionary: in 2 volumes. M.: Nedra. Edited by K. N. Paffengolts et al. 1978 ... Geological Encyclopedia
Modern Encyclopedia
- (anaerobic organisms) are able to live in the absence of atmospheric oxygen; some types of bacteria, yeast, protozoa, worms. Energy for life is obtained by oxidizing organic, less often inorganic substances without the participation of free ... ... Big Encyclopedic Dictionary
Anaerobes- (from the Greek an negative particle, aer air and bios life), organisms that can live and develop in the absence of free oxygen; some types of bacteria, yeast, protozoa, worms. Obligate, or strict, anaerobes develop ... ... Illustrated Encyclopedic Dictionary
Organisms (mainly prokaryotes) that can live in the absence of free oxygen in the environment. Obligate A. receive energy as a result of fermentation (butyric acid bacteria, etc.), anaerobic respiration (methanogens, sulfate-reducing bacteria ... Dictionary of microbiology
Ow, pl. (unit anaerobe, a; m.). Biol. Organisms capable of living and developing in the absence of free oxygen (cf. aerobes). ◁ Anaerobic, oh, oh. Ah, bacteria. Ah, the infection. * * * anaerobes (anaerobic organisms), able to live in the absence of ... ... encyclopedic Dictionary
I Anaerobes (Greek negative prefix an + aēr air + b life) are microorganisms that develop in the absence of free oxygen in their environment. They are found in almost all samples of pathological material with ... ... Medical Encyclopedia
Anaerobic organisms, anaerobionts, anoxybionts (from the Greek an negative particle and Aerobes), organisms that can live and develop in the absence of free oxygen and receive energy for life by splitting ... ... Great Soviet Encyclopedia
ANAEROBES- (from the Greek an negative particle, aer air and bios life), organisms that can live and reproduce in the absence of atm. oxygen. They receive energy for life by splitting Ch. arr. organic substances without the participation of free oxygen. Veterinary Encyclopedic Dictionary
Anaerobes are organisms that obtain energy in the absence of oxygen access by substrate phosphorylation. The term "anaerobes" was introduced by Louis Pasteur, who discovered butyric fermentation bacteria in 1861.
All microorganisms according to the type of respiration are divided into aerobic and anaerobic. Anaerobic respiration is a set of biochemical reactions that occur in the cells of living organisms when other substances (for example, nitrates) are used as the final proton acceptor, and refers to energy metabolism processes (catabolism, dissimilation), which are characterized by the oxidation of carbohydrates, lipids and amino acids to low molecular weight compounds.
If an organism is able to switch from one metabolic pathway to another (for example, from anaerobic to aerobic respiration and vice versa), then it is conditionally referred to as facultative anaerobes. Until 1991, in microbiology, a class of capneistic anaerobes was distinguished that required a low concentration of oxygen and a high concentration of carbon dioxide (Brucella bovine type - B. abortus). A moderately strict anaerobic organism survives in an environment with molecular O2, but does not reproduce. Microaerophiles are able to survive and multiply in an environment with a low partial pressure of O2. If an organism is not able to "switch" from anaerobic to aerobic respiration, but does not die in the presence of molecular oxygen, then it belongs to the group of aerotolerant anaerobes. For example, lactic acid and many butyric bacteria. Obligate anaerobes die in the presence of molecular oxygen O2 - for example, representatives of the genus of bacteria and archaea: Bacteroides, Fusobacterium, Butyrivibrio, Methanobacterium). Such anaerobes constantly live in an oxygen-deprived environment. Obligate anaerobes include some bacteria, yeasts, flagellates and ciliates.
Toxicity of oxygen and its forms for anaerobic organisms
An oxygen rich environment is aggressive towards organic life forms. This is due to the formation of reactive oxygen species in the course of life or under the influence of various forms of ionizing radiation, which are much more toxic than molecular oxygen O2. The factor determining the viability of an organism in an oxygen environment is the presence of a functional antioxidant system capable of eliminating: superoxide anion (O2−), hydrogen peroxide (H2O2), singlet oxygen (O), and molecular oxygen (O2) from the internal environment organism. Most often, such protection is provided by one or more enzymes: superoxide dismutase, which eliminates the superoxide anion (O2−) without energy benefits for the body; catalase that eliminates hydrogen peroxide (H2O2) without energy benefits for the body; cytochrome - an enzyme responsible for the transfer of electrons from NAD H to O2. This process provides a significant energy benefit to the body. Aerobic organisms most often contain three cytochromes, facultative anaerobes - one or two, obligate anaerobes do not contain cytochromes. Additional antioxidant protection can be provided by the synthesis or accumulation of low molecular weight antioxidants: vitamin C, A, E, citric and other acids.
Anaerobic microorganisms are the normal microflora of the human body, while in 30-100% of cases they can be the cause of pyoinflammatory diseases.
The presence of anaerobic bacteria in the test material should be suspected under the following criteria: Bad smell of the test sample, Localization of infection near the mucous membrane, Infection after a human or animal bite, Gas in the test material, Previous treatment with drugs that are inactive against anaerobes (antibiotics: aminoglycosides, old quinolones, trimethoprim), Black staining of blood-containing exudates, Presence of "sulfur granules" in secretions, Unique morphology on Gram stain, Absence of growth under aerobic conditions of microorganisms seen in micropreparations from exudate, Growth in the anaerobic zone of the nutrient medium, Anaerobic growth on selective media for anaerobes, Characteristic colonies on anaerobic agar plates, Fluorescence of colonies in ultraviolet light.
Microbiological diagnostics. Currently, the main diagnostic methods are bacteriological with extended identification by biochemical properties, as well as gas chromatography (chemotaxonomy) and PCR (gene diagnostics).
Cultivation of anaerobic organisms. For the cultivation of anaerobes, special methods are used, the essence of which is to remove air or replace it with a specialized gas mixture (or inert gases) in sealed thermostats - anaerostats. Another way to grow anaerobes (most often microorganisms) on nutrient media is to add reducing substances (glucose, sodium formic acid, casein, sodium sulfate, thiosulfate, cysteine, sodium thiogluconate, etc.) that bind peroxide compounds toxic to anaerobes.
General nutrient media for anaerobic organisms. For the general medium of Wilson - Blair, the base is agar-agar with the addition of glucose, sodium sulfite and ferrous chloride. Clostridia form black colonies on this medium by reducing sulfite to a sulfide anion, which combines with iron (II) cations to give a black salt. As a rule, black colony formations on this medium appear in the depth of the agar column. The Kitt-Tarozzi medium consists of meat-peptone broth, 0.5% glucose, and pieces of liver or minced meat to absorb oxygen from the medium. Before sowing, the medium is heated in a boiling water bath for 20-30 minutes to remove air from the medium. After sowing, the nutrient medium is immediately filled with a layer of paraffin or paraffin oil to isolate it from oxygen access. GasPak - the system chemically provides a constancy of the gas mixture acceptable for the growth of most anaerobic microorganisms. In a sealed container, water reacts with sodium borohydride and sodium bicarbonate tablets to form hydrogen and carbon dioxide. Hydrogen then reacts with oxygen in the gas mixture on a palladium catalyst to form water, which is already re-reacting with the hydrolysis of borohydride. This method was proposed by Brewer and Olgaer in 1965. The developers introduced a disposable hydrogen generating sachet, which was later upgraded to carbon dioxide generating sachets containing an internal catalyst.
Classification anaerobic bacteria is based on the principles of genotypic homology, which allows to determine the phylogenetic relationship, in addition, all anaerobes can be classified according to morphology and relation to Gram color.
Gram-positive: rods (Clostridium, Bifidobacterium, Lactobacillus, Mobiluncus), cocci (Anaerococcus, Peptococcus, Peptostreptococcus, Coprococcus). Gram-negative: rods (Bacteroides, Porphyromonas, Prevotella, Fusobacterium, Leptotrichia), cocci (Acidaminococcus, Veillonella, Megasphaera).
Let us consider representatives of the main taxonomic groups of great medical importance.
Gram-positive spore-forming rods.
spore-forming bacteria of the genusClostridium
Spore-forming anaerobes of the genus Clostridium There are over 150 species. Spores are round or oval in shape, located in the center of the cell subterminally or terminally, depending on the species of the microbe. The diameter of the spore is usually larger than the diameter of the cell, so the cell containing the spore looks swollen and resembles a spindle (from lat. clostridium- spindle). These bacteria, under favorable conditions, can cause gas gangrene, tetanus, botulism, pseudomembranous ulcerative enterocolitis, food poisoning and other diseases associated with clostridial lesions of various organs and systems in humans.
obligate anaerobes are, obligate anaerobes are representativesObligate (strict) anaerobes- organisms that live and grow only in the absence of molecular oxygen in the environment, it is detrimental to them.
Metabolism
It is widely believed that obligate anaerobes die in the presence of oxygen due to the absence of the enzymes superoxide dismutase and catalase, which process the deadly superoxide formed in their cells in the presence of oxygen. Although this is true in some cases, however, some obligate anaerobes have been found to have the activity of the aforementioned enzymes, and genes responsible for these enzymes and related proteins have been found in their genomes. Such obligate anaerobes include, for example, Clostridium butyricum and Methanosarcina barkeri. Yet these organisms are unable to exist in the presence of oxygen.
There are several other hypotheses to explain why strict anaerobes are sensitive to oxygen:
- Decomposing, oxygen increases the redox potential of the environment, and a high potential, in turn, inhibits the growth of some anaerobes. For example, methanogens grow at a redox potential of less than -0.3 V.
- Sulfide is an integral component of some enzymes, and molecular oxygen oxidizes sulfide to disulfide and thereby disrupts the activity of the enzyme.
- Growth can be inhibited by the lack of electrons available for biosynthesis, since all the electrons go to reduce oxygen.
It is most likely that the sensitivity of strict anaerobes to oxygen is due to these factors in combination.
Instead of oxygen, obligate anaerobes use alternative electron acceptors for cellular respiration, such as: sulfates, nitrates, iron, manganese, mercury, carbon monoxide (CO). For example, sulfate-reducing bacteria, which are found in large numbers in the bottom marine sediments, cause the smell of rotten eggs in these places due to the release of hydrogen sulfide. The energy released by such breathing processes is less than by oxygen respiration, and the above alternative electron acceptors do not provide an equal amount of energy.
Representatives
Bacteroides and Clostridium are examples of non-spore-forming and spore-forming strict anaerobes, respectively.
Other examples of obligate anaerobes are Peptostreptococcus, Treponema, Fusiform, Porphyromonas, Veillonella and Actinomyces.
Notes
- Kim, Byung Hong and Geoffrey Michael Gadd. Bacterial Physiology and Metabolism. Cambridge University Press, Cambridge, UK. 2008.
- ANAEROBIC BACILLI (inaccessible link - history). Retrieved March 10, 2009. Archived from the original on January 29, 2009.
|
||||||||||||||||||||||||||||||||||||||||||||||||
obligate anaerobes and, obligate anaerobes representatives, obligate anaerobes are
