The stench of cesspools and dumps, rotting organic remains - all this causes a persistent feeling of disgust in people. But, when the first reaction passes, and common sense turns on, the understanding comes that this is an obligatory process of life. Behind any decay, you can see the nascent new life. This is the eternal cycle of substances in nature. And no matter how diverse the living organisms on the planet, it is surprising that the only ones that are responsible for decomposition are the bacteria of decay.
What is decomposing
Decomposition processes are the whole range of reactions, as a result of which complex substances decompose into simpler and more stable ones. The process of putrefaction (ammonification) is called decomposition to simple molecules organic matter containing nitrogen and sulfur. A similar process - fermentation - is the decomposition of nitrogen-free organic substances - sugars or carbohydrates. Both processes are carried out by microorganisms. The elucidation of the mechanism of these processes began with the experiments of Louis Pasteur (1822-1895). If we look at the bacteria of putrefaction exclusively from a chemical point of view, we will see that the causes of these processes are instability organic compounds and microorganisms act only as causative agents chemical reactions. But both protein, and blood, and animals under the influence of bacteria undergo different types of decay, then the dominant role of microorganisms is undeniable.
The study of the subject continues
Decay is of great importance both in the economy of nature and in human activity: from technical production to the development of diseases. Applied bacteriology was born only about 50 years ago, and the difficulties of study are still enormous today. But the prospects are huge:
Who are these destructors?
Bacteria is a whole kingdom of unicellular prokaryotic (not having a nucleus) organisms, which reads about 10 thousand species. But this is known to us, and in general the existence of more than a million species is assumed. They appeared on the planet long before us (3-4 million years ago), they were its first inhabitants, and it was largely thanks to them that the Earth became suitable for the development of other life forms. For the first time, in 1676, the Dutch naturalist Anthony van Leeuwenhoek saw "animalcules" in his own hand-made microscope. Only in 1828 did they get their name from the work of Christian Ehrenberg. The development of magnifying technology allowed Louis Pasteur in 1850 to describe the physiology and metabolism of decay and fermentation bacteria, including pathogens. It was Pasteur, the inventor of the anthrax and rabies vaccine, who is considered the founder of bacteriology, the science of bacteria. The second outstanding bacteriologist is the German physician Robert Koch (1843-1910), who discovered Vibrio cholerae and tubercle bacillus.
So simple and so complex
The shape of the bacteria can be spherical (cocci), straight rods (bacilli), curved (vibrio), spiral (spirilla). They can unite - diplococci (two cocci), streptococci (a chain of cocci), staphylococci (bunch of cocci). The cell wall of murein (a polysaccharide combined with amino acids) gives shape to the body and protects the contents of the cell. The cell membrane of phospholipids can invaginate and contain complexes of organs of movement (flagella). The cells do not have a nucleus, but the cytoplasm contains ribosomes and circular DNA (plasmids). There are no organelles, and the functions of mitochondria and chloroplasts are performed by mesosomes - protrusions of the membrane. Some have vacuoles: gas vacuoles perform the function of moving in the water column, and storage contains glycogen or starch, fats, polyphosphates.
How do they eat
According to the type of nutrition, bacteria are autotrophic (they synthesize organic substances themselves) and heterotrophic (consume ready-made organic substances). Autotrophs can be photosynthetic (green and purple) and chemosynthetic (nitrifying, sulfur bacteria, iron bacteria). Heterotrophs are saprotrophs (they use waste products, dead remains of animals and plants) and symbionts (they use the organic matter of living organisms). Decay and fermentation are carried out by saprotrophic bacteria. Some bacteria need oxygen to carry out metabolism (aerobes), while others do not need it (anaerobes).
Our armies cannot be counted
Bacteria live everywhere. Literally. In every drop of water, in every puddle, on rocks, in air and soil. Here are just a few of the groups:
Optimal conditions
Certain conditions are necessary for putrefaction, and it is the deprivation of these conditions of bacteria that lies at the heart of our cooking (sterilization, pasteurization, canning, and so on). For an intensive decay process, it is necessary:
- The presence of the bacteria themselves.
- External conditions - humid environment, temperature +30-40 °C.
Various options are possible. But water is an essential attribute of the hydrolysis of organic substances. And enzymes work only in a certain temperature regime.
Main ammonifiers
Decay bacteria living in the soil of the earth are the most common group of prokaryotes. They are playing important role in the nitrogen cycle and return minerals (mineralize) to the soil, which are so necessary for plants for photosynthesis processes. The shape of bacteria, their relationship to the presence of oxygen and the ways of feeding are diverse. The main representatives of this group are spore-forming clostridia, bacilli and non-spore-forming enterobacteria.
Stages of organic decomposition
The stages of decomposition of organic substances by decay bacteria are quite complex from a chemical point of view. In general, this process is carried out as follows:
hay stick
The most studied bacterium is Bacillus subtilis, a very effective ammonifier. Only E. coli (Escherichia coli), our intestinal symbiont, has been better studied. Hay bacterium is an aerobic decay bacterium. On its surface are protease catalytic enzymes produced by bacteria and used to obtain vital energy. Proteases enter into hydrolysis reactions with proteins of the environment and destroy its peptide bonds with the release of the beginning of large chains of amino acids, and then smaller ones. Everything she needs goes into the cage, and what she doesn't need is given away. And toxic substances remain - hydrogen sulfide and ammonia. It is because of these gases that the habitats of hay sticks smell so unpleasant.
Our neighbours
About 50 trillion different microorganisms live in our intestines, which is about two kilograms. And this is 1.5 times more than the total number of cells in the entire human body. And who is the master here, and who is the symbiont? This is, of course, a joke. But among this variety of neighbors there are also decay bacteria. The benefits and harm to the body from them depend on their number and pathogenicity. There are up to 40,000 bacteria in our mouths. The acidic environment of our stomach can withstand lactobacilli, some streptococci and sarcins. Pancreatic juice with aggressive digestive enzymes (lipases and amylases) is released into the duodenum and makes it almost completely sterile.
In the small and large intestines, the environment is alkaline, the entire mass of microflora is concentrated here. It is here that bacteria help us absorb vitamins (bifidobacteria), synthesize vitamins (K and B) and suppress pathogenic flora (E. coli), break down starch and cellulose, proteins and fats (ammonifying bacteria) and this is not the whole list of useful functions of our neighbors. With feces, each person excretes about 18 billion bacteria, which is more than people on the entire planet. But the same bacteria can, under certain conditions, cause disease. That is why many of them are considered conditionally pathogenic.
The Importance of Rot Bacteria
The first living organisms of this planet, the most effective in terms of occupying all the ecological niches existing on the planet Earth, are bacteria. They mineralize the soil, making it fertile. Return inorganic substances to the cycle. Dispose of the corpses and waste products of all living organisms on the planet. Provide for mankind natural resources. They make our life easier and help in the assimilation of food components. This list can be continued for a long time. Of course, the negative value of putrefactive bacteria is also great. But nature knew what it was doing and our task on this planet is not to upset the delicate balance that the world around us has come to in these almost four million years.
Bacteria undoubtedly produce a process of putrefaction, fermentation, accompanied by the exhalation of gases, and this we find in all carnivorous fish in the stomach. It can even be harmful to the body by irritating the intestines. Nevertheless, even if we recognize a certain role for bacteria in the process of preliminary decomposition of food substances in the intestines of fish, they absolutely cannot be considered substitutes for enzymes, and therefore they must be recognized as replacing pepsin, which we will discuss below.[ ...]
Rotting (methane fermentation) is a process that occurs without access to atmospheric oxygen, in which organic substances under the action of various symbiotic organisms, passing through big number intermediate products decompose to methane and carbon dioxide. The last stage of decomposition occurs under the action of methane bacteria.[ ...]
Bacteria live everywhere - in soil, water, air, in organisms of plants, animals and humans. Many bacteria are heterotrophic organisms in terms of nutrition, i.e., they use ready-made organic substances. Some of them, being saprophytes, destroy the remains of dead plants and animals, participate in the decomposition of manure, and contribute to soil mineralization. Bacterial processes of alcohol, lactic acid fermentation are used by man. There are species that can live in the human body without causing harm. For example, E. coli lives in the human intestine. Certain types of bacteria, settling on food, cause spoilage. Saprophytes include decay and fermentation bacteria.[ ...]
In the process of decay of plant and animal corpses, denitrifying bacteria convert nitrates into free nitrogen (N)2 -> F)a -» N20 -> N2, which escapes into the atmosphere, but nitrogen-fixing bacteria again convert atmospheric nitrogen into organic compounds available for assimilation by plants.[ ...]
lower organisms. Sludge decay stops at a formaldehyde concentration of 100 mg/l. Aerobic decomposition processes stop at a formaldehyde concentration of 135-175 mg/l. The maximum harmful concentration for Escherichia coli bacteria is 1 mg/l, for Scenedesmus algae - 0.3-0.5 mg/l and for crustaceans 2 mg/l. Organisms involved in methane fermentation can become accustomed to formaldehyde and then tolerate a 15% concentration of formaldehyde. The resulting gas has equimolecular parts of CH4 and CO2.[ ...]
lower organisms. For Escherichia coli bacteria, the maximum harmful concentration is 0.1 mg / l. Sludge decay processes are greatly delayed if the nickel concentration in raw sludge exceeds the limit of 500-1000 mg/l. According to Rudolfs, the concentration of 500 mg/l Ni does not affect the decay process; a concentration of 1000 mg/l Ni reduces putrefaction by 35%, a concentration of 2000 mg/l - by 95%. The growth of Scenedesmus algae is retarded if the concentration exceeds 0.9 mg/l Ni; the maximum harmful concentration for crustaceans is 6 mg/l.[ ...]
In addition, the anaerobic bacteria Spirillum desulfuricans, during the decay of plant elements and in the presence of sulfate salts, release hydrogen sulfide, which in the Black Sea, due to the lack of circulation, is accumulated in the depths; from 150 soot. in such quantity that all life ceases there.[ ...]
With vitality anaerobic bacteria the processes of decay of the components of plant and microbial cells are associated with the formation of also simple, but incompletely oxidized organic, and then mineral compounds (see the general scheme of these processes on p. 126).[ ...]
Bacterial diseases are caused by highly infectious bacteria. In connection with the transition to mechanized harvesting, which causes mechanical damage to tubers, the damage to potatoes by bacterioses has increased. As a result of the defeat of these diseases, the death of plants in the field, the rotting of planting tubers and the new crop in the field, and their rotting during storage are observed. Yield losses can reach 50%.[ ...]
Due to the activity of thermophilic bacteria, the temperature of manure rises to 50-70°C. Carbon dioxide and water vapor released during decay take part in the reactions of formation of white lead. As a result of the processes taking place in the pots, about 70-80% of the lead is converted into white. After unloading the pots, the basic carbonate is separated from the metallic lead. This operation used to be done by hand, but is now done with special machines and wet mills. White is separated from lead residues by elutriation, after which they are washed from excess lead acetate, filtered and dried. Lead white according to the indicated method was previously produced not in buildings, but in heaps, and therefore this method is also called heap, and white is sometimes called lag white (a corrupted Dutch word loog is a room for the production of lead white).[ ...]
In both cases, both during smoldering and decay, ammonia is formed. This ammonia is then oxidized with the help of other aerobic bacteria and passes first into nitrogenous, and then into nitric acid. Accordingly, these processes are called ammonification and nitrification.[ ...]
Soil microflora is very diverse. Here the bacteria perform various functions and are subdivided into the following physiological groups: decay bacteria, nitrifying, nitrogen-fixing, sulfur bacteria, etc. Among them are aerobic and anaerobic forms.[ ...]
In livestock complexes, ammonia is formed from the decay of organic compounds under the action of ureazoactive anaerobic bacteria. The activity of these bacteria increases with increasing temperature. Therefore, in summer, as a rule, the concentration of ammonia is much higher than in winter.[ ...]
Nitrogen is returned to the atmosphere again with the gases released during decay. The role of bacteria in the nitrogen cycle is such that if only 12 of their species involved in the nitrogen cycle are destroyed, life on Earth will cease. American scientists think so.[ ...]
REDUCERS - organisms whose main result of nutrition is decay or other decomposition of complex compounds into simpler ones. First of all fungi and bacteria.[ ...]
Phenolic glycosides of moss and lichen cells prevent their decay, and after death they contribute to the formation of peat. Phenolic lichen acids inhibit the growth of many bacteria and molds, so many lichens are practically sterile and were used in northern hospitals during the Great Patriotic War as a cushioning material when bandaging rai.[ ...]
Mineralization processes are carried out with the obligatory participation of bacteria: in the first case, aerobic, developing in the presence of air (oxygen) and contributing to the process of oxidation and formation of acids, and in combination with potassium and sodium - mineral salts (carbonic, nitrate, sulphate or phosphate, as well as carbonic acid CO2); in the second case, anaerobic, developing in the absence of air and contributing to the processes of decay - the splitting of complex organic substances, which are accompanied by the release of foul-smelling gases, explosive (methane) and small amounts of carbon dioxide CO2, the transition of sulfur to hydrogen sulfide H /; -. nitrogen - to ammonia NH3. In addition, an environment conducive to the spread of infectious microbes is created.[ ...]
Only those bacteria that cause decay and do not need oxygen to decompose organic matter survive, the product of their vital activity is the emitted hydrogen sulfide. Thus, not only the lake is dying, but also adjacent ecosystems as a result of hydrogen sulfide poisoning.[ ...]
Infectious plant diseases caused by bacteria, fungi, and 51 viruses are widespread. The most common forms of these diseases are: raids on the surface of leaves, shoots (gray rot, etc.), twisting of leaves, rotting of roots and stems.[ ...]
Soft collar rot is caused by Erwinia cartovora. The disease is detected during hot weather. Bacteria live in the earth; penetrate into plants when the roots are damaged as a result of tillage. Rotting of the root neck is accompanied by an unpleasant odor.[ ...]
During fermentation, a partial precipitation of flakes of protein substances occurs. However, the acidic reaction and the presence of lactic acid bacteria prevent the development of putrefactive bacteria, which contribute to the further process of decomposition of substances. Only after the acids formed have been neutralized can the wastewater be subjected to the process of putrefaction. To keep warm Wastewater it is necessary to provide a heated room.[ ...]
BACTERIAL FERTILIZERS - fertilizers containing useful for page - x. plants soil microorganisms (eg nitragin). BACTERIA [gr. bakleria - stick] - a group of microscopic unicellular microorganisms that have cell wall, but without a formed nucleus, devoid of chlorophyll and plastids, multiplying by division. B. are widespread in nature (cause decay, fermentation, etc.), participate in the biogeochemical cycle of all biologically important chemical elements, performing the function of decomposers. Many key processes of the cycle are carried out only with the help of B. (for example, nitrification, denitrification, nitrogen fixation, oxidation and reduction of sulfur compounds, etc.). B. - causative agents of many diseases of humans, animals and plants (typhus, cholera, tuberculosis). BACTERIOLOGICAL POLLUTION - see Art. Biological pollution, as well as Coli-index and Microbial number.[ ...]
Biological ponds (clarifiers) are used for weakly concentrated wastewater containing organic substances easily decomposed by bacteria. They are also used as secondary clarifiers for chemically treated or incompletely biologically treated wastewater. Their dimensions must be selected in such a way that the waste water in them is not subjected to the process of decay at any time. These dimensions are calculated on the basis of the biochemical oxygen demand, which must be covered by air, and sometimes by dilution with oxygen-rich water. If these natural replenishments of oxygen are insufficient, then its deficiency is eliminated by the addition of nitrates. The calculation can be based on the equivalent of the population, and for each inhabitant it is necessary to count 20 m? pond area. In order for assimilation under the influence of light to proceed completely, it is necessary that the depth of the pond does not exceed 1.20 m.[ ...]
In practice great importance has "biochemical decomposition of proteins. The process of decomposition of proteins or their derivatives under the influence of putrefactive bacteria is called decay. The processes of decay can occur aerobically and anaerobically. Decay is accompanied by the release of pungent-smelling substances: ammonia, hydrogen sulfide, skatole, indole, mercaptans, etc. [... ]
Mineralization - the process of destruction (decay) of organic substances, i.e., their transition to mineral ones, proceeds in nature under the influence of bacteria and microorganisms called aerobic. If there is a lot of oxygen in a watercourse or soil, then the individual constituent elements of organic substances - nitrogen, carbon, sulfur, phosphorus - are oxidized to mineral salts of nitric, carbonic, sulfuric and phosphoric acids. With an insufficient amount or absence of oxygen, slow decomposition (rotting) of organic substances occurs. As a result, methane CSH, hydrogen sulfide LbE, and ammonia K]H3 are formed. The process proceeds under the influence of bacteria called anaerobic.[ ...]
Cyanoethylated cotton has high rot and mildew resistance. When kept for a very long time in soil contaminated with bacteria that cause cellulose decay, this product retains its full strength (and in some cases even some increase was observed). Cyan-ethyl-proven cotton and manila hemp also do not rot, being in water for a long time. Rot resistance increases with increasing nitrogen content and becomes absolute when it reaches 2.8-3.5%. However, the presence of even small amounts of carboxyl groups (formed as a result of saponification of cyanoethyl groups) adversely affects the resistance of cellulosic materials to the action of putrefactive bacteria. Therefore, it is very important to carry out cyanoethylation under the mildest conditions. Alkaline treatments should also be reduced or avoided altogether when washing, bleaching and dyeing cyanoethylated cotton.[ ...]
When plants are diseased, tubers, as a rule, do not form before flowering. With a later disease, tubers are formed, but sick with a black leg, their decay during storage continues. They create a hotbed of infection in the vault. In the soil, black leg bacteria do not persist for a long time.[ ...]
When diluted at 1:100,000, sublimate prevents rotting. Germination of anthrax spores is inhibited by a concentration of 3 mg/L. Sublimate harms spirogyram even at a dilution of 1:100,000,000. The maximum harmful concentration for Escherichia coli bacteria is 2 mg/l, for See-nedesmus algae and Daphnia magna crustaceans - 0.03 mg/l.[ ...]
Methane, hydrogen, hydrogen sulfide and other gases, accumulating in structures built on closed landfills, form explosive mixtures, the filtrate contains decay products of garbage. For example, at the Rostov-on-Don landfill, the degree of bacterial pollution of groundwater exceeded the average values for city sewerage: 1 ml of water contained up to 1.5 million bacteria, including 34,000 intestinal bacteria.[ ...]
When discharged into water bodies of sewage of some chemical industries, polluted with hydrogen sulfide, there is an abundant development of filamentous sulfur bacteria belonging to the genera ThioWinx. and Veddla1: oa- These bacteria form fouling on the bottom and near the shores of the reservoir. Pollution of water bodies with sewage containing iron ferrous salts is accompanied by the development of fouling of filamentous iron bacteria - LeptoWnx, Clyatylbnx, and CtactoWnx. Dying off, such fouling is deposited in deeper pits and, being subjected to decay processes, cause flashes of secondary pollution.[ ...]
But a significant part of the dead organic matter, including the actual detritus, for example, the remains of vegetation - wood, cannot be eaten by detritophages, but rots and decomposes in the process of feeding fungi and bacteria.[ ...]
In addition to increasing the efficiency of cotton pickers, pre-harvest leaf removal contributes to earlier ripening of the crop (by 15-20 days). Under the action of defoliants, the spread of pathogenic bacteria, fungi, insects, which often cause rotting of raw cotton on leafy plants in late autumn, is also limited.[ ...]
We saw above what huge masses of various organic substances are brought into the reservoir from land, but probably an even greater amount of them comes from aquatic plants and animals. Let us see what processes they undergo in order to re-enter the cycle of life. Putrefaction caused by microbes begins with the dissolution of protein and the formation of albumoses and peptones, which quickly decompose and eventually give ammonia, carbon dioxide, hydrogen, methane, hydrogen sulfide, water, and so on. Thus, the whole process takes place with the help of the vital activity of the three groups.[ ...]
Sirp; indicates that when preliminarily untreated effluents are discharged into the reservoir, sphlego1u1u51 ans grows very intensively. Mac Gauhey showed that the discharge of 260 m3 of wastewater in 1 sec. into the Roanax River in Virginia (USA) caused cloudiness in it, the formation of a sulfide odor, yellow silt at the bottom of the river, the occurrence of decay processes, a significant increase in BOD5 and carbon dioxide, a decrease in the number of bacteria in the river and the disappearance of fish.[ ...]
Polysaprobic organisms are characteristic of very polluted waters, which contain a lot of proteins, hydrogen sulfide, methane and carbon dioxide. There is no dissolved oxygen in such waters. In this group of organisms certain types a little, but each species develops very intensively. Basically, the group includes bacteria (millions in 1 ml of water), ciliates, colorless flagella, sulfur bacteria. There is a lot of organic detritus in bottom sediments; aquatic flowering plants are absent. The polysaprobic zone is characterized by regenerative processes of decay and decay.[ ...]
Excessively developed vegetation impedes the proper operation of ponds, contributes to the deterioration of the hydrochemical and gas regimes, especially at night, when oxygen is consumed by all aquatic organisms for breathing and its deficiency is created. During the decomposition of dying vegetation, toxic decay products (ammonia, hydrogen sulfide, etc.) are released, and its remains are a substrate for the preservation and reproduction of saprophytic and pathogenic fungi, bacteria.[ ...]
There are three types of dust: mineral (inorganic), organic and cosmic. Weathering and destruction of rocks, volcanic eruption, steppe and peat fires, evaporation from the surface of the seas cause the formation of mineral dust. Organic dust in the air is represented by aeroplankton - organisms living in the atmosphere (bacteria, fungal spores, plant pollen, etc.), and products of decay, fermentation and decomposition of plants and animals. Cosmic dust formed from the remains of burnt meteorites during their passage through the atmosphere.[ ...]
But if too much nutrients enter the reservoir (for example, the effluents of a mineral fertilizer plant are systematically discharged), the cycle is disrupted. The rapid growth of algae begins, the thickness of their layer increases sharply, the flow of light into the lower layers of the reservoir decreases, and the processes of photosynthesis slow down. At the same time, the decay of a large mass of dead cells intensifies. Their decomposition takes all the oxygen dissolved in water and then not only animals die, but also detritus-decomposing bacteria. The chain is broken. If the effluents harmful to the reservoir are not stopped, then the natural mechanism of self-purification will decline.[ ...]
S. is also possible in populations of species with a secondary behavioral strategy, but it is less pronounced and is combined with miniaturization (with high density some individuals drop out of the population, and the rest are smaller). SELF-PURIFICATION OF NATURAL WATERS (S.p.v.) - a variant of biotic transformation of the environment, the process of purification of water from pollutants by their decomposition and precipitation. S.p.v. occurs both in anaerobic environment (rotting) and in aerobic. In the latter case, the S.r.p. occurs more actively, the higher the content of oxygen in the water. In S.p.v. in addition to bacteria, fungi, algae, and animals also take part. In running water S.p.v. occurs more actively than in a standing one. When a large amount of wastewater enters the reservoirs (this takes place in major cities RF) ability to S.p.v. reservoirs is insufficient. Special treatment facilities and reduction of discharges through the use of low-waste technologies are needed. SANITARY PROTECTIVE ZONE - an area planted with forest and separating enterprises that pollute the atmosphere from the residential part locality.[ ...]
Thus, antibiotics have all the properties that are necessary for medicinal preparations used in crop production. There are numerous reports in the literature about the successful use of antibiotics in the fight against various plant diseases. At the same time, it was shown that antibiotics not only protect the plant from damage, but also have a therapeutic effect in the presence of various infections (phytopathogenic fungi, bacteria and actinomycetes). Antibiotic drugs have been tested in the treatment of diseases of fruit trees, cotton, grain and vegetable crops, ornamental plants both in laboratories and under production conditions. For example, good results have been obtained with the use of aureo-fungin in the fight against fungal diseases of seeds and downy mildew. Pre-sowing treatment of cotton seeds with an antibiotic made it possible to reduce the diseases of cotton with gommosis and verticillium wilt by 5-6 times. The use of antibiotics in plant budding is promising. Antibiotic-treated cuttings are practically sterile, and the plants do not become ill after grafting, while untreated controls often die from infection. The use of antibiotics is very effective in diseases of plants of bacterial origin: bacteriosis of apple and pear trees, walnut rot, bacterial spot of tomatoes and peppers, wet rot of potatoes, bacterial spot of legumes, bacteriosis of tobacco, rotting of potato plantings, brown rot of cabbage stalk, bacterial spot of chrysanthemums, etc. d.[ ...]
Cellulosic materials are subject to the action of cellulolytic enzymes during operation. Under the action of these enzymes, cotton, wood, paper, cellophane film, viscose silk are easily destroyed; acetate fibers and film are resistant to degradation due to high degree substitution of hydroxyl groups in the macromolecule of this cellulose ether. Modification of cellulose, aimed at improving its basic properties, often increases the resistance to decay. Thus, treatment with various reagents in order to impart crease resistance to cellulosic materials at the same time causes the resistance of the material to decay. Sometimes unexpected problems arise. For example, the development of paper with improved wet strength has resulted in used paper not degrading in conventional wastewater treatment plants. Newer waterborne paints contain carboxymethylcellulose or methylcellulose as a thickener. Therefore, a slight growth of a fungus or bacteria is sufficient to cause the destruction of these thickeners, as a result of which the paints liquefy and: collapse.[ ...]
At the beginning of our century, a microbiological theory of aging arose, the creator of which was I. I. Mechnikov, who distinguished between physiological and pathological old age. He believed that human old age is pathological, that is, premature. The basis of the ideas of I. I. Mechnikov was the doctrine of orthobiosis (Orthos - correct, bios - life), according to which the main cause of aging is damage nerve cells products of intoxication resulting from putrefaction in the large intestine. Developing the doctrine of a normal lifestyle (observance of hygiene rules, regular work, abstinence from bad habits), I. I. Mechnikov also proposed a way to suppress putrefactive intestinal bacteria by consuming fermented milk products.[ ...]
The initial stage of fish spoilage is muscle autolysis, which is expressed in the softening of tissues under the influence of enzymes, and then the breakdown of proteins to amino acids. Under the influence of microflora, their further decay can occur, up to the final deterioration of fish meat and the appearance of ammonia and hydrogen sulfide. Enzymes that cause autolysis in fish, on average, are much larger than in the tissues of warm-blooded animals. So, in the warm season, in a non-gutted herring, the speed with which autolysis occurs may seem stunning. Since the activity of the bacteria in the fish is revived simultaneously with the changes that have come about under the influence of enzymes, these changes should be postponed as far as possible. True, in the process of autolysis, bad-smelling and unpleasant-tasting substances do not yet appear in the fish, as is observed with decay caused by bacteria. But from the point of view of fish storage, autolysis is undoubtedly a negative phenomenon.[ ...]
In a well-organized compost pile, organic matter is completely decomposed. At the same time, the temperature inside the compost heap reaches 70 ° C. In the process of overturning, the contents of the compost pile are permeated big amount fungal threads. High temperatures and antibiotics produced by fungal growths kill disease-causing microbes in the heap. Compost heaps should be well ventilated. The contents of the heap should be shoveled from time to time. In this case, the upper layers will fall inside the heap and, thus, the entire contents of the heap will warm up well and evenly. When providing air access to the inside of the heap, no rotting processes occur, and bacteria, fungi and other organisms decompose the waste. Holes for air to enter the compost heap are easy to make by sticking wooden stakes into the middle of the heap. Such ventilation, together with the ventilation that occurs during shoveling, contributes to the proper overheating of the contents of the heap.
Material from the Forensic Medical Encyclopedia
Decay is a complex process of decomposition of organic compounds, primarily proteins, under the influence of microbes. It usually begins on the second or third day after death. The development of decay is accompanied by the formation of a number of substances: biogenic diamines (ptomains), gases (hydrogen sulfide, methane, ammonia, etc.), which have a specific, unpleasant odor. The intensity of the decay process depends on many factors. The most important temperature environment and humidity. Rotting occurs quickly at an ambient temperature of +30 - +40C. In air, it develops faster than in water or soil. The corpses in the coffins rot even more slowly, especially when they are sealed. The process of decay slows down sharply at a temperature of 0-1 ° C, at a lower temperature it can completely stop. Putrefactive processes are significantly accelerated in cases of death from sepsis (blood poisoning) or in the presence of other purulent processes.
Putrefaction usually begins in the large intestine. If the corpse is in normal room conditions (+16 - +18 ° C), then on the skin, in places of the large intestine closer to the anterior abdominal wall (iliac regions - lower lateral parts of the abdomen), spots appear on the 2nd-3rd day green (corpse green), which then spread throughout the body and cover it entirely on the 12th-14th day.
The gases formed during decay impregnate the subcutaneous tissue and inflate it (cadaveric emphysema). Particularly swollen are the face, lips, mammary glands, abdomen, scrotum, limbs. The body at the same time significantly increases in volume. Due to the decay of blood in the vessels, the venous network begins to appear through the skin in the form of branched figures of a dirty green color, clearly visible during external examination of the corpse. Under the influence of gases, the tongue can be pushed out of the mouth. Under the surface layer of the skin, putrefactive blisters are formed, filled with bloody fluid, which eventually burst. The gases formed during decay in the abdominal cavity can even push the fetus out of the uterus of a pregnant woman and at the same time turn it out (post-mortem birth).
In the process of decay, the skin, organs and tissues gradually soften and turn into a fetid, mushy mass, bones are exposed. Over time, all soft tissues melt and only one skeleton remains from the corpse. Depending on the burial conditions (the nature of the soil, etc.), the complete destruction of soft tissues and the skeletonization of the corpse occurs approximately within 3-4 years. In the open air, this process ends much faster (in the summer - within a few months). The bones of the skeleton can be preserved for tens and hundreds of years. Dead bodies in the ground change their hair color.
Approximate terms of development of putrefactive changes
| 1. Resolution of rigor mortis | Start of day 3 |
| 2. Cadaverous greens in the iliac regions | |
| A) outdoors in summer | 2-3 days |
| B) at room temperature | 3-5 days |
| 3. Cadaverous greens of the entire skin of the abdomen | 3-5 days |
| 4. Corpse greens of the entire skin of a corpse (if there are no flies) | 8-12 days |
| 5. Putrid venous network | 3-4 days |
| 6. Pronounced putrefactive emphysema | 2nd week |
| 7. The appearance of putrid blisters | 2nd week |
| 8. Putrid destruction (if there are no flies) | 3 months |
The rate of development of putrefactive processes is largely determined by environmental conditions. Casper proposed a rule (see Casper's rule), according to which a corpse reaches the same state in three environments in a certain pattern. Thus, the registered processes of decay a week after the onset of death when the corpse is in the air correspond to the two-week prescription of the corpse in the water, and eight weeks ago when the corpse is in the ground.
Provided that the temperature of the corpse is equal to or slightly higher than the ambient temperature (by 1-1.5 ° C), the solution to the issue of determining the duration of the time interval required for the appearance of signs of decay at a particular tissue temperature is carried out according to the formula:
τ \u003d 512 / (TC - 16.5)
where τ is the duration of decay of the object under study, hour; T С – medium temperature, °С.
Putrefaction is the decomposition of proteins by microorganisms. This is damage to meat, fish, fruits, vegetables, wood, as well as processes occurring in soil, manure, etc.
In a narrower sense, putrefaction is considered to be the process of decomposition of proteins or protein-rich substrates under the influence of microorganisms.
Proteins are an important component of living and dead organic world are found in many foods. Proteins are characterized by great diversity and complexity of structure.
The ability to destroy protein substances is inherent in many microorganisms. Some microorganisms cause a shallow cleavage of the protein, others can destroy it more deeply. Putrefactive processes constantly occur in natural conditions and often occur in products and products containing protein substances. Protein degradation begins with its hydrolysis under the influence of proteolytic enzymes released by microbes into the environment. Rotting proceeds in the presence of high temperature and humidity.
Aerobic decay. Occurs in the presence of atmospheric oxygen. The end products of aerobic decay are, in addition to ammonia, carbon dioxide, hydrogen sulfide and mercaptans (which have the smell of rotten eggs). Hydrogen sulfide and mercaptans are formed during the decomposition of sulfur-containing amino acids (cystine, cysteine, methionine). Among the putrefactive bacteria that destroy protein substances under aerobic conditions is also the bacillus. mycoides. This bacterium is widely distributed in the soil. It is a mobile spore-forming rod.
anaerobic decay. Occurs under anaerobic conditions. The end products of anaerobic decay are the decarboxylation products of amino acids (removal of carboxyl group) with the formation of foul-smelling substances: indole, akatol, phenol, cresol, diamines (their derivatives are cadaveric poisons and can cause poisoning).
The most common and active causative agents of decay under anaerobic conditions are Bacillus puthrificus and Bacillus sporogenes.
The optimal development temperature for most of the putrefactive microorganisms is in the range of 25-35°C. Low temperatures do not cause their death, but only stop development. At a temperature of 4-6°C, the vital activity of putrefactive microorganisms is suppressed. Non-spore putrefactive bacteria die at temperatures above 60°C, and spore-forming bacteria withstand heating up to 100°C.
The role of putrefactive microorganisms in nature, in the processes of food spoilage.
In nature, decay plays a large positive role. It is an integral part of the circulation of substances. Putrefactive processes ensure the enrichment of the soil with such forms of nitrogen that are necessary for plants.
A century and a half ago, the great French microbiologist L. Pasteur realized that without the microorganisms of decay and fermentation, which turn organic matter into inorganic compounds, life on Earth would become impossible. The largest number of species of this group live in the soil - there are several billion of them in 1 g of fertile arable soil. The soil flora is mainly represented by decay bacteria. They decompose organic remains (dead bodies of plants and animals) into substances that plants consume: carbon dioxide, water and mineral salts. This process on a global scale is called the mineralization of organic residues, the more bacteria in the soil, the more intense the process of mineralization, therefore, the higher the fertility of the soil. However, putrefactive microorganisms and the processes they cause in the food industry cause spoilage of products, and especially of animal origin and materials containing protein substances. In order to prevent spoilage of products by putrefactive microorganisms, such a storage regime should be provided that would exclude the development of these microorganisms.
To protect food from decay, sterilization, salting, smoking, freezing, etc. are used. However, among the putrefactive bacteria there are spore-bearing, halophilic and psychrophilic forms, forms that cause spoilage of salted or frozen products.
Topic 1.2. Influence of environmental conditions on microorganisms. Distribution of microorganisms in nature.
Factors affecting microorganisms (temperature, humidity, medium concentration, radiation)
Plan
1. Effect of temperature: psychrophilic, mesophilic and thermophilic microorganisms. Microbiological bases of food storage in chilled and frozen form. Thermal stability of vegetative cells and spores: pasteurization and sterilization. Effect of heat treatment of food products on the microflora.
2. Influence of humidity of a product and environment on microorganisms. The value of relative air humidity for the development of microorganisms on dry products.
3. Influence of the concentration of dissolved substances in the habitat of microorganisms. The influence of radiation, the use of UV rays for air disinfection.
The influence of temperature: psychrophilic, mesophilic and thermophilic microorganisms. Microbiological bases of food storage in chilled and frozen form. Thermal stability of vegetative cells and spores: pasteurization and sterilization. Effect of heat treatment of food products on the microflora.
Temperature is the most important factor for the development of microorganisms. For each of the microorganisms there is a minimum, optimum and maximum temperature regime for growth. According to this property, microbes are divided into three groups:
§ psychrophiles - microorganisms that grow well at low temperatures with a minimum at -10-0 °C, an optimum at 10-15 °C;
§ mesophiles - microorganisms for which the optimum growth is observed at 25-35 °C, the minimum - at 5-10 °C, the maximum - at 50-60 °C;
§ thermophiles - microorganisms that grow well at relatively high temperatures with an optimum growth at 50-65 °C, a maximum at temperatures above 70 °C.
Most microorganisms belong to mesophiles, for the development of which the temperature of 25-35 °C is optimal. Therefore, the storage of food products at this temperature leads to the rapid multiplication of microorganisms in them and the deterioration of products. Some microbes with significant accumulation in foods can lead to human food poisoning. Pathogenic microorganisms, i.e. that cause human infectious diseases are also mesophiles.
Low temperatures slow down the growth of microorganisms, but do not kill them. In chilled food products, the growth of microorganisms is slow, but continues. At temperatures below 0 ° C, most microbes stop multiplying, 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 fall into a state similar to anabiosis, retain their viability, and continue their development when 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 be stored in frozen meat for a long time, and after defrosting meat, under favorable conditions, they quickly accumulate to a dangerous amount for humans.
When exposed to high temperatures, exceeding the maximum endurance of microorganisms, their death occurs. Bacteria that do not have the ability to form spores die when heated in a humid environment to 60-70 ° C after 15-30 minutes, to 80-100 ° C - after a few seconds or minutes. Bacterial spores are much more resistant to heat. They are able to withstand 100 ° C for 1-6 hours, at a temperature of 120-130 ° C bacterial spores die in a humid environment in 20-30 minutes. Mold spores are less heat resistant.
Thermal culinary processing of food products in catering, pasteurization and sterilization of products in the food industry lead to partial or complete (sterilization) death of vegetative cells of microorganisms.
During pasteurization, the food product is subjected to a minimum temperature effect. 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 min) 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 the release of 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 by ultra-high temperature treatment (at temperatures above 130 °C) within a few seconds, which allows you to save all the beneficial properties of milk.
