Putrefaction

PUTREFACTION, the decomposition of protein and other nitrogenous substances under the influence of putrefactive bacteria (see below), accompanied by the formation of foul-smelling products. The development of putrefactive processes is promoted by: a sufficient degree of moisture, proper osmotic pressure, appropriate temperature, a reaction close to neutrality, and the absence of antiseptic substances. Under the influence of putrefaction, proteins undergo very numerous, profound, and complex changes, as a result of which the protein molecule breaks down into a long series of smaller molecules. The beginning of the chemical study of protein putrefaction processes was laid by Nencki, Baumann, the Salkowski brothers, Gautier, Etard, and Brieger (Nencki, Baumann, Salkowski, Gautier, Etard, Brieger). Putrefactive cleavage takes place with the participation of enzymes produced by microorganisms, and, as in the case of protein hydrolysis by mineral acids, leads through the stages of albumoses, peptones, and less complex peptides to amino acids. Whereas protein cleavage under the influence of mineral acids stops at the formation of amino acids, putrefactive processes prove to be more complex, lead to a further, deeper breakdown of proteins, and present in this respect a rather significant similarity to protein decomposition under the influence of heating with dry caustic alkali at 250°. Processes of putrefactive protein breakdown can proceed in the following directions: 1) hydrolysis (see Proteins), 2) deamination, the removal of the amino group from amino acids, 3) the removal of carbon dioxide from the carboxyl group, 4) reduction by hydrogen released during putrefaction, 5) oxidation by the oxygen of air or water. Depending on the predominance of aerobic or anaerobic microorganisms, the character of putrefactive processes can be very diverse. With sufficient access to air, putrefactive processes take on the character of decay and more complete oxidation. As a result of the combined action of the above-mentioned chemical processes, a very complex mixture of diverse products of protein molecule putrefaction is formed. Thus, tyrosine split off from the protein during putrefaction — H0.C₆H₄.CH₂.CH(NH₂).C00H — yields oxyphenyl-lactic acid HO.C₆H₄.CH₂.CH(OH).C00H, from which is then formed coumaric acid HO.C₆H₄.CH:CH. .COOH and oxyphenyl-propionic acid HO.C₆H₄.CH₂.CH₂. COOH; further appears oxyphenyl-pyruvic acid HO.C₆H₄.CH₂.CO.COOH, passing into oxyphenyl-acetic acid H0.C₆H₄.CH₂.C00H, cresol HO.C₆H₄.CH₃, oxybenzoic acid HO.C₆H₄.COOH, phenol HO.C₆H₅; by the splitting off of CO₂ from tyrosine, tyramine HO.C_eH₄.CH₂.CH₂.NH₂ is formed. Similar complex changes are undergone by other cyclic groups of the protein molecule: phenylalanine, tryptophan (characteristic products of its putrefaction are skatole and indole), and histidine. Under the influence of putrefaction, ring cleavage can occur; for example, from tryptophan anthranilic acid is formed. During the putrefaction of acyclic amino acids, acids (volatile fatty acids, from caproic to formic) and their corresponding amines also appear; for example, from leucine (CH₃)₂CH.CH₂.CHNH₃.COOH are formed isocaproic acid (CH₃)₂CH.CH₂.CH₂.COOH and isoamylamine (CH₃)₂CH.CH₂.CH₂.NH₂. The products of cystine putrefaction are: ethyl sulfide CH₃.CH₂.S.CH₂.CH₃ and the gaseous methyl mercaptan CH₃SH and hydrogen sulfide H₂S, possessing a very foul odor. Among other gases developing during protein putrefaction are CO₂, H₂, CH₄, NH₃, CH₃.NH₂, (CH₃)₂NH, and (CH₃)₃N. These methylated amines belong to an extensive group of putrefaction products having the character of organic bases and known under the name of ptomaines (see) or cadaveric alkaloids. Some ptomaines (tyramine, phenylethylamine, histamine, cadaverine, putrescine, etc.) arise as a result of the simple splitting off of CO₂ from the corresponding amino acids, whereas the formation of other ptomaines involves more complex processes, including synthetic ones. Many ptomaines possess toxic properties. In addition to ptomaines, other toxic substances, toxins (see), are formed during putrefaction. For the first time, Panum in 1856 extracted a boiling-resistant "putrefactive poison" from putrefying protein. Some of the putrefactive toxins have the character of enzymes or protein bodies. The putrefaction of phosphoproteins leads to the cleavage of their protein molecule in the same direction as in simple proteins. In addition, phosphoric acid is split off, from which phosphine may then be formed. Purine bases are split off from nucleoproteins; among them, guanine and adenine pass into hypoxanthine and xanthine under the influence of microbial desamidase. During putrefaction under aerobic conditions, a part of the formed purine bases is converted into uric acid by the action of oxidase, upon the putrefaction of which urea and ammonium carbonate are formed. Lecithins upon putrefaction undergo saponification with the formation of fatty acids, glycerin, phosphoric acid, and choline, from which trimethylamine is then split off, imparting a herring-like odor to decomposing objects of animal and vegetable origin. Other products of choline putrefaction are: toxic neurine and muscarine, methylamine, NH₃, methane, and CO₂. Cholesterol C₂₇H₄₆O under the influence of putrefactive processes is reduced to coprosterol C₂₇H₄₈O. Urea during the putrefaction (alkaline fermentation) of urine passes under the influence of urease into ammonium carbonate. Putrefaction is of very important significance in the balance of matter in nature. Upon the putrefaction of corpses (see) of animals and dead plants, as well as waste products of plants and animals (leaves, urine, feces, etc.), their complex organic constituents, disintegrating, turn into simplest mineral substances: NH₃, nitrous and nitric acids, CO₂, water, sulfuric and phosphoric acids. These substances then, entering the atmosphere, precipitation, and soil, serve as nutrients for plants, which use them for the synthesis of complex organic substances and the creation of new living cells. In this way, a circulation of matter is established between the mineral, plant, and animal worlds, which is absolutely necessary for the possibility of the continuation of life on earth. At the same time, putrefactive processes eliminate the accumulation of dead organisms on land and in water. By turning animal and plant waste into manure and humus, putrefaction is an important factor in soil fertilization. Putrefactive processes are also of importance in the formation of silt and therapeutic muds. In the intestine of animals, chiefly in the large intestines, putrefaction takes place as a normal phenomenon, while under normal conditions putrefaction in the intestine does not proceed as intensively as one might expect under those conditions favorable for the development of putrefaction that exist in the intestine. One of the factors reducing the intensity of putrefactive processes in the intestine is competition between putrefactive microorganisms and other microbes. Aside from food and the products of its digestion, the constituent parts of digestive juices also undergo putrefaction in the intestine. Putrefactive microorganisms, on the one hand, partly contribute to the digestion of food substances by the action of the enzymes they produce, but, on the other hand, have an unfavorable and even harmful significance for the organism, because they cause the complete decomposition of a certain part of the food substances entering the intestine and the products of their digestion, while substances toxic to the organism also arise. The toxic products of putrefaction formed in the intestine, being absorbed and entering with the blood of the portal vein into the liver, are retained by it to a greater or lesser degree and little by little destroyed or converted into non-toxic compounds for the organism (phenylsulfuric, cresylsulfuric, indoxylsulfuric acids, paired glucuronic acids, urea); some products of putrefaction pass through the organism and are excreted by the kidneys unchanged. An abnormal course of putrefactive processes in the intestine, qualitatively or quantitatively, can cause phenomena of poisoning of the organism (autointoxication of intestinal origin). An intensification of putrefactive processes in the intestine occurs during constipation, peritonitis, and certain other diseases, especially during intestinal obstruction. An indication of the intensification of putrefactive processes is the increase in the urine of the amount of animal indican and other ethereal sulfuric acids. Under pathological conditions, putrefaction can occur in other places of the organism besides the intestine (putrefaction of food in the stomach in the absence of free HCl, putrefactive breakdown of tumors, tissues in gangrene, effusions, etc.). Putrefactive processes are also of importance in technology, as they develop, for example, during the retting of flax, the manufacture of certain varieties of cheese, and others.

Biological wastewater treatment is based on the joint action of anaerobic and aerobic putrefaction processes. Eliminating the possibility of putrefaction is of great practical importance (in food technology and in some other branches of technology), which is achieved through drying, curing, smoking, increasing osmotic pressure (by adding salt or sugar), cooling, acidification (with acetic or lactic acids), and sterilization (by heating or adding antiseptic substances). V. Gulievich.

Putrefactive bacteria are the agents of the decomposition of dead protein matter into the simplest chemical compounds. The nitrogen of the protein molecule is ultimately liberated in the form of NH₃ or free N. Putrefaction represents one of the phases of the nitrogen cycle in nature. The NH₃ liberated during protein decomposition dissolves in soil water and is then oxidized by nitrifying bacteria to nitric acid salts. These salts are suitable for plant nutrition and serve them for the synthesis of the protein molecule. Plant protein in turn serves for animal nutrition and for the synthesis of animal protein. In this way, the nitrogen cycle and the cycle of life associated with it are closed. The number of bacteria possessing the ability to destroy proteins (proteolytic action) or split albumoses and peptones (peptolytic action) is very large, but in many bacteria the putrefactive function is only secondary; therefore, putrefactive bacteria should be considered those in which the proteo- or peptolytic function is primary. Among aerobes, Proteus vulgaris Hauser (see Figure 1) belongs to such bacteria in the first place, characterized by the following properties: it has the form of a small (1–1.2 µ), motile, peritrichous rod, Gram-negative; on agar, Proteus vulgaris grows forming a film on the surface of the medium; it rapidly destroys gelatin, coagulated serum, and egg white; it ferments glucose with the formation of gas. In second place in prevalence in nature are the "soil" types of putrefactive bacteria: Bac. subtilis, Bac. mycoides, Bac. mesentericus, Bac. ramosus, having the shape of rather large rods (2–3 µ), Gram-positive, spore-forming, located in the center of the rod. These bacteria destroy proteins, but are inactive with respect to carbohydrates. Pigment bacteria can be attributed to the third group, among which... as energetic a protein destroyer as Proteus. Flavobacterium aromaticum has the shape of a small rod (0.6–1 µ), non-motile, Gram-negative. On agar, it grows in the form of large, moist, yellow, pleasantly smelling colonies. This rod is frequently found in the intestine during pathological processes. Pigment peptolytic bacteria include Bact. pyocyaneum Gessard and Bac. fluorescens liquefaciens Flügge; they have the shape of small rods (1–2 µ), are Gram-negative, motile due to the presence of a single polar flagellum, and secrete a blue-green (B. pyocyaneum) or green (B. fluorescens) pigment. B. pyocyaneum readily multiplies in the pus of wounds and in intestinal contents during enteritis as a putrefactive microbe. B. fluorescens is an aquatic bacterium with proteolytic and peptolytic functions. To the peptolytic bacteria very frequently encountered in putrefaction, especially in the intestine, belongs Bac. faecalis alcaligenes Petruschky, having the shape of a slender rod 2–3 µ long, pale-staining with aniline dyes, Gram-negative, motile due to the presence of a tuft of flagella located at the pole. This rod is inactive towards carbohydrates; it splits albumoses and peptone with the formation of alkali. On agar, it grows in the form of round, transparent colonies. It does not liquefy gelatin and does not curdle milk. From the Bact. coli group, the specifically putrefactive bacterium is Bac. cloacae Jordan, which has the morphological and cultural properties of the colon bacillus, and in addition, proteolytic ones. Bac. cloacae is found in the intestines of humans and animals, as well as in sewage and polluted waters. Among cocci, the specifically putrefactive can be considered: 1. Diplococcus magnus anaerobius Tissier and Martelli, a very large Gram-positive coccus growing on nutrient media under anaerobic conditions; found in putrefying meat and also in intestinal contents. 2. Sarcina flava de Bary, an aerobic sarcina, exceptionally widespread in nature, vigorously destroying proteins, constantly encountered in putrefactive processes. The processes of destruction of organic substances in soil take place with the constant participation of actinomycetes. Among anaerobic bacteria, the first place among putrefactive bacteria is occupied by Bac. putrificus Bienstock, having the shape of a straight, long (5–6 µ), motile, peritrichous rod forming a round or oval spore at the end (see Figure 2). Under anaerobic conditions, it vigorously destroys proteins with the release of a putrid odor. It is found in putrefying meat, corpses, intestinal contents, etc. A variety of Bac. putrificus is represented by Bac. sporogenes Metchnikoff, having the shape of a short and thick rod (see Figure 3) with a spore located closer to one of the ends of the rod. Bac. perfringens Veillon and Zuber has the shape of a large, thick rod (5–6 µ long), Gram-positive, non-motile, spore-bearing (see Figure 4); it is widely distributed in nature, constantly present in intestinal contents, soil, and milk. It is easily cultivated under anaerobic conditions from material preheated to 80–90°. It has the ability to decompose proteins and carbohydrates with the formation of butyric acid and a gas consisting of a mixture of N, H, and CO₂. Bac. perfringens has pathogenic properties: it was described by Frankel as the causative agent of gas phlegmon. According to Tissier, Bac. perfringens can cause diarrhea in infants. The putrefaction of a corpse or meat proceeds with a definite succession of microorganisms, depending on changes in the properties of the decomposing protein medium. Initially, under aerobic conditions, putrefaction occurs in the presence of Proteus vulg., B. coli, Streptoc. pyogenes, Sarcina flava, and other cocci. After 3–4 days they are replaced by anaerobes capable of developing in the presence of sugars: Bac. perfringens, Bac. bifermentatus sporog.; after 1–8 days strict anaerobes develop: Bac. putrificus, Bact. putridum, Microc. anaerobius, and other rarer putrefactive anaerobic microorganisms. Putrefaction of milk occurs mainly with the participation of Bac. perfringens, which splits carbohydrates and lactic acid with the formation of butyric acid and simultaneously decomposes milk proteins. The products of protein cleavage are further destroyed by Bac. faecalis alcaligenes and Proteus Zenkeri. The causative agents of egg putrefaction are a group of bacteria of the Bac. oogenes hydrosulfureus type, which converts the white and yolk into a mushy mass smelling of H₂S; putrefaction ends with Bac. oogenes fluorescens, which converts the egg mass into a liquid with a fecal odor. The processes of putrefaction in human intestinal contents occur during diseases accompanied by the release of blood and pus into the cavity of the intestinal tract (dysentery, ulcerative processes) or during digestive disorders on the basis of insufficient secretion of digestive glands or overloading of the intestine with food masses. Constipation can also cause stagnation and putrefaction of intestinal contents. Metchnikoff attributed a major role to putrefactive processes in the large intestines in the origin of premature aging. In his opinion, such protein decomposition products as indole and skatole chronically poison the body and cause the development of blood vessel sclerosis. Apparently, putrefactive processes in the intestine arise not as an independent process, but as a secondary one, as a result of insufficient internal secretion and the associated external secretion of the digestive glands.