Putrefaction

putrefaction: see decay of organic matter.

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putrefaction [‚pyü·trə′fak·shən]

(biochemistry)

Decomposition of organic matter, particularly the anaerobic breakdown of proteins by bacteria, with the production of foul-smelling compounds.

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Putrefaction 

the decomposition of complex nitrogen-containing organic compounds (primarily proteins) caused by the action of putrefactive microorganisms. Because putrefaction is accompanied primarily by the evolution of gaseous ammonia, putrefaction is also called ammonification, and the microorganisms involved in the process are called ammonifiers. Putrefaction is a complex, multistep biochemical process. It develops in various ways and has various results, depending on the chemical nature of the substrate, the availability of oxygen, and on the microfloral composition. Specific groups of microbes prevail at various stages of putrefaction.

Among the putrefactive microorganisms the most important are anaerobes and facultative anaerobes, which contain powerful proteolytic enzymes, as well as aerobic sporogenous bacteria of the genus Bacillus and nonsporogenous bacteria of the genus Pseudomonas. Mold fungi are also involved in putrefaction, but the role of actinomycetes is insignificant. The majority of putrefactive bacteria are saprophytes, some of which are capable of hydrolyzing live tissues, giving rise to various diseases (for example, gas gangrene in animals and humans and soft rots of plants).

Putrefaction plays an important role in the cycle of materials in nature. The life activity and death of animals causes a large amount of protein-containing products to enter the soil and bodies of water. These products are not accumulated because of the activity of putrefactive microflora but are mineralized. Thus, they may be used again by plants. By means of proteolytic enzymes (proteases and peptidases), putrefactive bacteria degrade proteins to polypeptides and then to amino acids, which undergo deamination and decarboxylation by the action of many microorganisms. Deamination results in the evolution of gaseous ammonia and the formation of saturated and unsaturated fatty acids and aromatic acids, as well as ketonic and hydroxy acids. Decarboxylation generates amines, many of which are very toxic. The amino acid radicals that are generated as a result of deamination and decarboxylation are further degraded. Thus, tryptophan forms skatole and indole, and the sulfur-containing amino acids methionine and cysteine form hydrogen sulfide. Fatty acids may ferment, evolving methane. Putrefaction in the absence of air involves predominantly reductive processes and the accumulation of many of the above-mentioned products. Free access to air allows completion of the process of putrefaction, all the carbon from the organic compounds being evolved in the form of carbon dioxide.

Putrefaction occurs in the intestinal tracts of animals as well as in soil and bodies of water. This is caused by anaerobes— Bacillus putrificus, B. perfringens, and B. sporogenes. The products of putrefaction are rendered harmless by the liver and are partly eliminated by the kidneys. In cases of constipation and obstructions of the intestinal tract poisoning may occur as a result of excessive absorption of the products of putrefaction. Lactic acid bacteria inhibit the putrefactive microflora of the intestinal tract.

Putrefactive bacteria cause food spoilage. In order to preserve foods from putrefaction, sterilization, pickling, smoking, freezing, and other techniques are used. However, putrefactive bacteria include sporogenous, halophilic, and psychrophilic forms that cause spoilage of pickled or frozen foods. Some industrial processes (removal of hair from animal skins, tanning of hides, and chemical cleaning of clothing) use enzyme preparations obtained from cultures of putrefactive microorganisms.

REFERENCES

Ierusalimskii, N. D. Osnovy fiziologii mikrobov. Moscow, 1963.
Metabolizm bakterii. Moscow, 1963. (Translated from English.)
Rabotnova, I. L. Obshchaia mikrobiologia. Moscow, 1966.

V. M. GORLENKO