Most bacteria are heterotrophs that are used. Nutrients Needed for Growth

For growth, maintenance of life and reproduction requires a variety of substances. In addition, a source of energy is needed. For the cultivation of microorganisms, a so-called nutrient-rich medium is used. Any culture medium should contain:

1. Carbon source for growth... Most bacteria, all fungi and protozoa are heterotrophs, that is, they need an organic carbon source. Typically, this source is glucose or an organic acid salt such as sodium acetate. In general, however, bacteria can use a wide variety of organic substances as a carbon source, including fatty acids, alcohols, proteins, carbohydrates, and methane. Certain soil bacteria and fungi, as well as a number of bacteria that live in the intestines of herbivores (eg ruminants), can metabolize cellulose and use it as a carbon source. All pathogenic bacteria are heterotrophs.
Algae and some bacteria, for example, cyanobacteria (blue-green algae) are autotrophs, that is, carbon dioxide is the source of carbon for them. Algae belong to photosynthetic organisms, while among bacteria there are both photosynthetic and chemosynthetic ones.

2. The nitrogen source can be organic, such as amino acids, peptides and proteins, or inorganic, such as ammonium salts or nitrates. Amino acids are usually added as solutions of partially digested proteins called peptones.

3. Growth factors, or vitamins, are sometimes necessary for the growth of microorganisms. Growth factors are equivalent to vitamins that animals need, and many of them are indeed vitamins. These are organic substances that are important for growth and are required in very small quantities. These include some B vitamins (thiamine, or B1; riboflavin, or B2; niacin, or B3 and Bb), and folic acid and para-aminobenzoic acid. For normal growth, only trace amounts of vitamins are required. In addition, other organic materials such as purines and pyrimidines may be required.
Microorganisms differ in their ability to synthesize their own growth factors from simpler substrates. If microorganisms are rather demanding on the growth conditions, then the media for their growth in the laboratory are prepared on the basis of natural substrates on which these microorganisms usually grow (such substrates include blood, soil, meat or yeast extracts).

4. Mineral salts... Most often, growth requires positively charged ions of calcium, potassium, sodium, iron and magnesium, as well as negatively charged chloride, phosphate (source of phosphorus) and sulfate ions (source of sulfur). As noted above, nitrogen is added in the form of ammonium or nitrate. The requirements for algae growth are about the same as for plant growth.

5. Energy source... The energy requirements of living cells were discussed at the beginning of one of the articles. Energy can be supplied in the form of chemical energy or light energy. An organism that consumes chemical energy is called chemotrophic; an organism that uses light energy is called phototrophic, or photosynthetic (Table 2.3). Photosynthetic microorganisms include algae and some bacteria, such as cyanobacteria. If chemical energy is needed, it is usually supplied in the form of sugar, such as glucose.

6. Water... Despite the fact that it is not literally a nutrient, water is essential for all living cells. Usually bacteria need more moisture than yeast, and yeast needs more than molds.

Nutrition is a kind of process by which the body receives the necessary energy and nutrients for cellular metabolism, repair and growth.

Heterotrophs: general characteristics

Heterotrophs are organisms that use organic food sources. They cannot create organic substances from inorganic ones, as is done in the process of photo- or chemosynthesis of autotrophs (green plants and some prokaryotes). That is why the survival of the described organisms depends on the activity of autotrophs.

It should be noted that heterotrophs are humans, animals, fungi, as well as part of plants and microorganisms that are incapable of photo- or chemosynthesis. I must say that there is a certain type of bacteria that use the energy of light to form their own organic matter. These are photoheterotrophs.

Heterotrophs get food different ways... But they all boil down to the main three processes (digestion, absorption and assimilation), in which complex molecular complexes are broken down to simpler ones and absorbed by tissues with subsequent use for the needs of the body.

Classification of heterotrophs

They are all divisible by 2 large groups - consumers and reducers. The latter are the final link in the food chain, since they are capable of converting into consumables are those organisms that use ready-made organic compounds that were formed during the life of autotrophs without their final transformation into mineral residues.

If we talk about the types of heterotrophic nutrition, then we should mention the holozoic species. Such nutrition, as a rule, is typical for animals and includes the following stages:

• Capturing food and swallowing it.
• Digestion. It involves breaking down organic molecules into smaller particles that dissolve more easily in water. It should be noted that first, food is mechanically ground (for example, with teeth), after which the action is carried out with special digestive enzymes (chemical digestion).
• Suction. Nutrients either immediately enter the tissues, or first into the blood, and then with its flow to various organs.
• Assimilation (assimilation process). It is about using nutrients.
• Excretion - excretion of end products of metabolism and undigested food.

Saprotroph organisms

As already noted, organisms that feed on dead organic debris are called saprophytes. To digest food, they secrete the appropriate enzymes, and then absorb substances resulting from such extracellular digestion. Fungi are heterotrophs, which have a saprophytic type of nutrition - for example, yeast or fungi Mucor, Rhizppus. They inhabit and secrete enzymes, and the thin and branched mycelium provides a significant absorption surface. In this case, glucose goes to the process of respiration and provides the mushrooms with energy, which is used for metabolic reactions. I must say that many bacteria are also saprophytes.

It should be noted that many compounds that are formed when saprophytes are fed are not absorbed by them. These substances enter the environment, after which they can be used by plants. That is why the activity of saprophytes plays an important role in the circulation of substances.

Symbiosis concept

The term "symbiosis" was introduced by the scientist de Bary, who noted that there are associations or close relationships between organisms of different species.

So, there are such heterotrophic bacteria that live in the digestive canal of herbivorous ruminants. They are able to digest cellulose by feeding on it. These microorganisms can survive in the anaerobic conditions of the digestive system and break down cellulose into simpler compounds that the host animals can independently digest and assimilate. Plants and root nodules of bacteria of the genus Rhizobium are another example of such symbiosis.

To summarize, it can be argued that heterotrophs are an extremely wide group of living things that not only interact with each other, but are also capable of influencing other organisms.

Heterotrophic bacteria, as a result of the decomposition of organic matter, receive energy for the synthesis of new cells, as well as for breathing and movement. A small part of the energy is lost in the form of heat. [...]

Another group of bacteria does not belong to the category of auto-trophic organisms; they oxidize thiosulfate to tetrathionate, but at the same time assimilation of carbon dioxide does not occur, and these bacteria are abligate heterotrophic; they represent the link between autotrophs and heterotrophs. [...]

Heterotrophic microorganisms, which cannot accumulate polyphosphates, but can compete for the substrate, especially for glucose if it is present in wastewater. In most cases, these bacteria are not involved in the biological removal of phosphorus. [...]

Heterotrophic microorganisms assimilate carbon only from ready-made organic compounds, but since there are countless organic compounds in nature, among heterotrophs there are species and even sometimes strains or groups of bacteria that assimilate carbon from certain classes of substances. [...]

Bacteria are the most common group of microorganisms in soil. Their number ranges from tens and hundreds of millions to several billions per gram of soil and depends on the properties of the soil and their hydrothermal conditions. Depending on the way of feeding, bacteria are divided into heterotrophic and autotrophic. In relation to the requirements for free oxygen, aerobic obligate (strict) bacteria are distinguished that require free oxygen; anaerobic - not using free oxygen. The latter are divided into obligate anaerobic, for which oxygen is toxic, and facultative anaerobic, insensitive to free oxygen. Bacteria carry out various processes of transformation of organic and mineral compounds in soils. [...]

Bacteria and actinomycetes can be conditionally attributed to plants, although, perhaps, they do not have direct relatives associated with other plants. The vast majority of bacteria are heterotrophic organisms. Only a few of them are chemotrophic. They synthesize organic matter due to the chemical energy released during the oxidation of inorganic compounds in their body. Among bacteria, unicellular ones prevail, but there are also filamentous multicellular organisms. Bacteria are capable of very rapid proliferation by division. Inside the cell of some bacteria, especially rod-shaped ones, a spore forms, which is released after the destruction of the bacterial membrane and, having its own protective membrane, remains viable even in extremely unfavorable conditions of temperature and humidity. Spores tolerate very low temperatures better than high temperatures. Their cells contain nuclear material (Fig. 4); they are capable of conjugation. [...]

The roles of bacteria in nature are very diverse, due to the different energy sources used by different groups of bacteria. Many heterotrophic aerobic bacteria are decomposers in ecosystems. In the soil, they participate in the formation of a fertile layer, transforming forest litter and decaying remains of animals into humus. Soil bacteria also break down organic compounds into minerals. It has been established that up to 90% of CO2 enters the atmosphere due to the activity of bacteria and fungi. Bacteria are involved in the biogeochemical cycles of nitrogen, sulfur, phosphorus. Self-purification of water in natural reservoirs, as well as wastewater treatment, is performed by aerobic and anaerobic heterotopic bacteria. [...]

Reducers are heterotrophic organisms (bacteria and fungi), final destructors that complete the decomposition of organic compounds to simple inorganic substances - water, carbon dioxide, hydrogen sulfide and salts. [...]

Reducers are heterotrophic organisms (bacteria, fungi) that receive energy by decomposing dead tissue or by absorbing dissolved organic matter released spontaneously or extracted by saprophytes from plants and other organisms. [...]

Most bacteria of the genus Pseudomonas have a heterotrophic type of metabolism, that is, they need ready-made organic matter to build a body. In this case, biosynthetic processes are carried out due to the exchange of the oxidative type, where oxygen is the final acceptor of electrons, the transfer of which is associated with the cytochrome system. Some representatives of this genus can exist due to anaerobic nitrate respiration, others use the energy of hydrogen oxidation. Many types of nseudomonads form pigments that are different in color and chemical nature; some synthesize vitamins, antibiotics, toxins. [...]

Heterotrophs (heterotrophic organisms) are organisms that use organic compounds (animals, fungi and most bacteria) as a carbon source. In other words, these are organisms that are not able to create organic substances from inorganic ones, but require ready-made organic substances. [...]

A number of peculiar microbes, first discovered by BV Perfiliev in the study of freshwater lakes, are also referred to as budding bacteria. These organisms are apparently responsible for the formation of lake ores. A typical stage in the development of Ме1о-genium is a microcolony, in the form of a spider, composed of radially diverging filaments covered with manganese oxidation. After the dissolution of manganese oxides, it is often possible to detect small budding cells connected by plasma filaments. A short stem grows on the thread, on which a bud is formed. The bud germinates and a spider-like microcolony reappears. [...]

The classification of bacteria is constantly a subject of discussion and controversy. This is due to the simplicity and uniformity of the structure and development and the lack of identification signs in prokaryotes. Biochemical characters widely used in microbiological classification are not stable in various natural conditions of the existence of a microbial population or in various artificial conditions of maintaining the strain. This biochemical instability is especially common in heterotrophic bacteria. [...]

Thus, bacteria are able to attack even such an inert metal as gold. Except TH. ferroox! clan8 and other thionic bacteria, which have an indirect effect, there are microorganisms capable of creating substances that enter into a water-soluble complex with gold. I. Paré isolated heterotrophic bacteria, which formed on organic media containing peptone and salts of organic acids, substances of unknown nature that dissolve gold. Under the influence of bacteria identified as you. Mgtiz and you. sphaensie, up to 10 mg / l of gold passed into the solution. It is possible that the decryption chemical nature The water-soluble gold complex will give the industry a new solvent. [...]

Nitrifying bacteria belong to the group of autotrophs that receive energy from chemical processes that occur with inorganic compounds, in contrast to phototrophs that use light energy, or from heterotrophs that assimilate carbon of organic compounds. Denitrifiers are heterotrophic bacteria; with a lack of oxygen, they assimilate the oxygen of nitrites and nitrates and use it to oxidize organic substances. The resulting nitrogen is liberated and returned to the atmosphere. Some types of microorganisms can reduce nitrates to ammonia. At present, in the processes of nitrogen circulation in nature, there is a lag of the processes of denitrification from fixation. [...]

The role of stem bacteria in nature is determined by their physiological characteristics as heterotrophic microorganisms capable of developing in depleted zones, where saprophytes, more demanding on food, are inactive. [...]

Denitrifying bacteria consume the same macronutrients as aerobic heterotrophic microorganisms. As a nitrogen source, in both cases, ammonium is preferable to nitrate. Urban wastewater usually does not have problems with macronutrients, but industrial wastewater can sometimes be depleted in phosphorus. [...]

Availability general types bacteria indicates that heterotrophic bacteria possess various types of metabolism, which makes it possible for activated sludge to quickly adapt to the treatment of various [...]

Most heterotrophic organisms receive energy as a result of biological oxidation of organic substances - respiration. Hydrogen from the oxidizable substance (see § 24) is transferred to the respiratory chain. If only oxygen plays the role of the final acceptor of hydrogen, the process is called aerobic respiration, and microorganisms are strict (obligate) aerobes that have a complete chain of transfer enzymes (see Fig. 14) and are able to live only with a sufficient amount of oxygen. TO aerobic microorganisms include many types of bacteria, gris-6¿i, algae, most of the protozoa. Aerobic saprophytes play a major role in the processes of biochemical wastewater treatment and self-purification of the reservoir. [...]

Switching hydrogen bacteria to a heterotrophic lifestyle usually reduces their ability to oxidize molecular hydrogen and fix carbon dioxide. However, not all organic substrates and not all hydrogen bacteria act on these processes in the same way. [...]

The species and generic composition of activated sludge bacteria is very diverse. An important task in its study is the correct selection of nutrient media, of which each individually cannot provide the growth of all inhabitants of activated sludge. In this regard, attempts have been made to study the nutritional requirements of microorganisms. Dyes and Bhat found that only 24% of 110 isolates obtained from untreated wastewater, and 8% of 150 strains isolated from activated sludge, do not need vitamins or amino acids when grown on a medium containing glycerol, sodium succinate and ammonium nitrate. Prekesem and Dondero showed that the total number of isolated bacteria is higher on agar medium with activated sludge extract as the sole source of nutrition than on other nutrient media. The effectiveness of the extract depends on the source and sample of the activated sludge. More than half of 127 strains isolated on a medium with activated sludge extract did not grow on synthetic media with glucose, amino acids, vitamins, yeast extract, and mineral salts. On the agarized extract of activated sludge, the number of grown bacterial colonies was 175.6 X Jub per 1 g of dry matter. Gayford and Richard obtained similar results using the sludge extract. At the same time, other researchers recommend casein-peptone-starch agar as the most suitable medium for isolating bacteria from waste and river water. However, on the other seven media used in the experiments, including those prepared on the basis of polluted waters, similar results were obtained. For quantitative accounting of microflora, homogenization of activated sludge before sowing on nutrient media is of great importance. For example, the use of ultrasound for this purpose led to a 20-fold increase in the number of cells of bacteria of the genus Thiobacillus and the total number of heterotrophic bacteria. [...]

REDUCTS, or destruents - heterotrophic organisms, Ch. arr. bacteria, fungi and protozoa that convert organic substances into inorganic compounds and close the biogenic cycle. WATER MODE [fr. regime] - change over time of levels, flows and volumes of water in water bodies and soils. [...]

Thus, among thionic bacteria, there are organisms with different potencies for an autotrophic and heterotrophic lifestyle. The reason why T. permeballis does not grow under autotrophic conditions is apparently that these bacteria do not form ribule diphosphate carboxylase and cannot fix carbon dioxide through the Calvin cycle. In T. meteriumsus, which, although growing on a mineral medium, but slowly, the activity of this enzyme is weak in comparison with other thionic bacteria growing under autotrophic conditions. Consequently, the limited ability of T. mbertecus to grow under autotrophic conditions and the lack of it in T. permelous are associated with the ability of these bacteria to use carbon dioxide to form various components of cells. [...]

Other strains of iron-oxidizing bacteria also grow heterotrophically. This property, however, is not universal for the entire group. The time of cell generation on glucose is about 4/2 hours, on an iron-containing medium - 10 hours. [...]

The values \u200b\u200bof the hydrolysis constants for heterotrophic bacteria under various conditions are presented in table. 3.2. [...]

Consumptions (consume), or heterotrophic organisms (heteros - another, trophe - food), carry out the process of decomposition of organic matter. These organisms use organic matter as a nutrient and energy source. Heterotrophic organisms are divided into phagotrophs (phaqos - devouring) and saprotrophs (sapros - rotten). [...]

At the first stage of biological purification, heterotrophic bacteria utilize organic nitrogen-containing components of fish excreta as an energy source and convert them into simple compounds, for example, ammonium. After organic compounds are converted into inorganic form by heterotrophic bacteria, biological treatment enters the stage of nitrification (biological oxidation of ammonium to nitrites and nitrates). It is carried out mainly by autotrophic bacteria. [...]

When treating industrial wastewater, heterotrophic bacteria play the main role in the destruction of organic matter contained in these waters both under aerobic and anaerobic conditions. The group of denitrifiers also belongs to heterotrophic bacteria, which develops in sewage treatment plants with a lack of oxygen and satisfies their need for it due to oxygen released during the reduction of nitrates and nitrites to free nitrogen - denitrification. This process is caused by various microorganisms found in the soil and in water bodies, and can be carried out only if there are organic compounds suitable for them in the waste fluid. [...]

Many heterotrophic organisms are capable of reducing manganese, but Bacillus circulans, you, have this ability to the greatest extent. polymyxa and sulfate-reducing bacteria. Manganese dissolves organic acids, formed by the bacterial route, and at the same time reduced to bivalent with the participation of nonspecific enzymes or such a reducing agent as hydrogen sulfide. Under the influence of bacteria reducing manganese, the forms of manganese are redistributed in silts, as well as in cocretions formed in ore-bearing lakes and deposits. [...]

It is believed that the first organisms, probably similar to bacteria, were heterotrophic anaerobes, capable of using organic substances of abiogenic origin. The formation of an electron transport chain allowed anaerobic bacteria to use those organic compounds that do not undergo fermentation as an energy source. The first heterotrophs gave rise to autotrophs, which were also anaerobes. Later, organisms capable of photosynthesis appeared among autotrophs, which led about 3.5-2 billion years ago to the conversion of CO2 into an organic compound and to the accumulation of oxygen in the atmosphere [...]

Typical representatives of tootbacteria are gram-negative non-spore-bearing bacteria, united in the Pseudomo-nadaceae family. The name of the family comes from two Greek roots: "pseudo" - similar and "monas" - the name of a group of protozoa (animals) with polar flagella. Therefore, pseudomonads include both rod-shaped bacteria with a polarized flagellum, and weakly curved rods, physiologically extremely specialized autotrophic chemosynthetic bacteria (Well-drogenomonas, Nitrosomonas, Thiobacillus) and ordinary heterotrophic bacteria (Pseudomo-nas), i.e. representatives mix, i.e., mix. nutrition - autotrophic and heterotrophic. [...]

In wastewater contaminated with organic compounds, the number of bacteria increases dramatically. Along with pathogenic species, saprophytic microorganisms, heterotrophic bacteria and fungi also develop, which decompose various organic compounds to mineral salts. [...]

Layered eukaryotic plants are also autotrophic, then they are called algae, and heterotrophic; there is no unifying generally accepted term for the latter. This category includes mushrooms and myxomycetes (slime molds). Often this category of heterotrophic lower plants is understood in a broad sense, attaching bacteria to them from the number of prokaryotic organisms. Similarly, the number of algae includes prokaryotic cyaneae, calling them blue-green algae. [...]

For a long time, it was believed that biological removal of phosphorus is carried out only by bacteria Aste (uba er. However, it is now well known that many heterotrophic microorganisms contained in wastewater and sludge of treatment facilities have the ability to accumulate phosphorus. bio-P-bacteria or phosphate-accumulating organisms (FAO). The mechanism of phosphorus accumulation is not always activated in bacteria, therefore, the determination of concentrations, for example, of bio-P-bacteria in wastewater can be difficult. In wastewater treatment plants with biological phosphorus removal, several groups of heterotrophic microorganisms competing for the substrate, especially for low molecular weight fatty acids, which are necessary for the implementation of the phosphorus-accumulating mechanism. Many of the competing bacteria are not FAO. It is the result of this competition that determines the success of the bio-P-process. [...]

The reaction rates in filtered water are higher, since the organic matter load is reduced, which favors the development of nitrifying bacteria as compared to heterotrophic bacteria. [...]

Biochemical oxidation determines the content of organic impurities in water that can be oxidized biochemically. Oxidation is carried out by aerobic heterotrophic bacteria. By analogy with COD, oxidizability using the oxidative capacity of bacteria is called biochemical oxygen demand, or BOD. [...]

There are three types of relationships between different groups of organisms in activated sludge that underlie the microbiological purification process: the metabiotic relationship between heterotrophic and nitrifying bacteria, the competitive relationship between heterotrophic bacteria and saprozoal protozoa, and the predator-prey relationship between ciliated protozoa and heterotrophic bacteria. [. ..]

Due to the massive structure of terrestrial plants, they form a large amount of persistent fibrous detritus (leaf fall, wood residues, etc.) that accumulates in the heterotrophic layer. In the phytoplankton system, on the contrary, the "rain of detritus" consists of small particles that are easier to decompose and are consumed by small animals. Therefore, it should be expected that the population of saprotrophic microorganisms in the soil will be more abundant than in bottom sediments under open water (Table 2). However, as we have already emphasized, the abundance and biomass of small organisms do not necessarily correspond to their activity; the metabolic rate and the turnover of a gram of bacteria can vary many times depending on conditions. In contrast to what is observed for producers and micro-consumables, the number and weight of macro-consumables in aquatic and terrestrial ecosystems are more comparable if the systems receive the same amount of energy. If large land grazing animals are included in the calculations, then the number and biomass of large mobile consumers, or “permeants” (nomads), will be almost the same in both systems (Table 2). [...]

Thiobacillus panevieu is capable of developing in a neutral reaction of the medium due to the oxidation of inorganic sulfur compounds and assimilation of CO2, and in the absence of inorganic sulfur - to a heterotrophic type of nutrition using organic substances. When this bacterium oxidizes thiosulfate to sulfate, the formation of elemental sulfur and polythionates as intermediate substances does not occur. [...]

These forms are found everywhere in terrestrial communities, but they are especially abundant in the uppermost soil layers (including the litter). The process of decomposition of plant residues, which consumes a significant proportion of the respiratory activity of the community, in many terrestrial ecosystems is carried out by a number of sequentially functioning microorganisms (Kononova, 1961). [...]

In addition to autotrophs and heterotrophs, there are organisms with a mixed type of nutrition. In some conditions, they feed as autotrophs, and in others - as heterotrophs. So, blue-green algae and some types of bacteria under sunlight carry out photosynthesis, that is, behave like photoautotrophs. In the absence of light, they switch to heterotrophic nutrition, that is, they become heterotrophs. [...]

T. feggooxidans are usually grown in mineral media containing carbon dioxide and reduced sulfur compounds or ferrous salts. Only recently have there been reports of the ability of some strains of these bacteria to grow on a medium with glucose in the absence of inorganic oxidizable substrates. However, the ability of T. ferrooxidans to switch to such a heterotrophic metabolism requires further study and verification. [...]

Prenuclear organisms - prokaryotes have all methods of feeding, are able to exist without oxygen in the atmosphere and without nitrogen compounds in the soil, and therefore they are pioneers in the conquest of lifeless spaces. Their role is both in the creation and in the destruction - the mineralization of organic matter. Thus, the bacterial kingdom holds the record for the variety of food methods: it is the only one in which there are representatives of all types of food. Bacteria - the oldest photoautotrophic organisms on the planet - include about 50 species. Heterotrophic bacteria play two main roles in the biosphere. The first is the decomposition of dead organisms and the return of the original elements to the environment. Much of this work takes place in digestive tracts multicellular animals. The second is the continuous involvement of new portions of minerals in the circulation. [...]

Decomposition includes both abiotic and biotic processes. However, usually dead plants and animals are decomposed by heterotrophic microorganisms and saprophages. This decomposition is the way bacteria and fungi obtain food for themselves. Decomposition, therefore, occurs through energetic transformations in and between organisms. This process is absolutely necessary for life, since without it all nutrients would be bound in dead bodies and no new life could not arise. IN bacterial cells and fungal mycelium, there are sets of enzymes necessary for the implementation of specific chemical reactions. These enzymes are released into dead matter; some of the products of its decomposition are absorbed by decomposing organisms for which they serve as food, others remain in the environment; in addition, some products are cleared from cells. Not a single species of saprotroph can accomplish complete decomposition of a dead body. However, the heterotrophic population of the biosphere consists of a large number of species, which, acting together, produce complete decomposition. Different parts of plants and animals are destroyed at different rates. Fats, sugars and proteins decompose quickly, while cellulose and plant lignin, chitin, hair and bones of animals are destroyed very slowly. Note that about 25% of the dry weight of grasses decomposed within a month, while the remaining 75% decomposed more slowly. After 10 months. there was still 40% of the original mass of herbs. The remains of the crabs had completely disappeared by this time. [...]

Depending on the nutritional level or as it is called the trophic level in the activated sludge, a gradual change in microflora and microfauna and a change in the nature of the relationship between sludge microorganisms are observed. When per unit mass of microorganisms there is a large amount of contamination - more than 300 mg of BOD total per 1 g of ashless substance per day, which corresponds to the first trophic level (highly loaded), then heterotrophic bacteria and protozoa compete in the sludge, which assimilate only dissolved impurities by reaction (3. 26). In this case, the number of species of the simplest microorganisms is small, and there is a quantitative predominance of any one of them.