Anaerobes

ANAEROBES (from Greek a- negative particle, aer- air and bios- life), microscopic organisms capable of deriving energy (see Anaerobiosis) not in oxidation reactions but in decomposition reactions of both organic compounds and inorganic ones (nitrates, sulfates, etc.). The prevalence of A. in nature and their role in the circulation of substances is enormous. They are found everywhere where decomposition of organic matter occurs without access to oxygen—in deep layers of soil, in sludge, in manure heaps, in ripening cheese, etc. A. are also found in well-aerated media in the case where aerobes are present there, which greedily bind free atmospheric oxygen. In the intestines of humans and animals, on the one hand, there are A. that are beneficial to the host, for example, Bifidobacterium bifidus, which plays the role of an antagonist towards the harmful flora, thanks to its ability to ferment both glucose and lactose with the formation of lactic acid; on the other hand, pathogenic A. are found there, causing putrefaction and various types of fermentation, which release toxins that are not indifferent to the organism, for example, B. putrificus, B. perfringens, etc. Among pathogenic microbes are known—B. tetani, perfringens, oedematis maligni, vibr. septique Pasteur's, B. sporogenes, aerofoetidus, etc. Many methods have been proposed for obtaining cultures of anaerobes, the general aim of which is to make the medium oxygen-free. This can be achieved by displacing O with other indifferent gases—H or N. O can also be removed by absorption, for which an alkaline solution of pyrogallol is used. Removal of O can be effected by pumping air out of a vessel with the medium using a water jet apparatus or a pump, or by pumping air from under a glass bell jar in which the seeded nutrient media are placed. One can combine two methods: pumping air out with simultaneous absorption of oxygen by an alkaline pyrogallol solution, for which Zlatogorov constructed a special apparatus. A simple method for obtaining individual colonies is the Vignal-Veillon method, in which the test material is mixed with melted and cooled to 43°C agar, drawn into a glass tube 30 cm long and 5-6 mm in diameter. The upper end of the tube is plugged with a cotton plug, and the lower end is drawn out; after filling, the lower end is sealed and the tube is placed in an incubator. The method of joint growth of aerobic and anaerobic microbes is also applied, by seeding for this purpose B. subtilis or B. mesentericus, which form a dense film on the surface of the medium and create conditions favorable for the growth of A. Media (containing pieces of fresh parenchymatous organs of animals) proposed by Tarrozzi and Naguchi are also fully suitable for culturing A., on which a layer of sterile paraffin oil is poured over the medium. For a rough separation of aerobic and anaerobic species, the Baird apparatus is used, which is a J-shaped tube, one end of which is drawn out fine, sealed, and bent down. The apparatus is completely filled with nutrient medium. In the medium seeded with material, aerobes will develop in the open end of the tube, while A. will develop in the closed end. By breaking off the sealed end of the tube, part of the liquid with the microbes contained in it can be released. Recently, a method has been proposed to chemically bind atmospheric oxygen with H. This method is the best, since it is easy to create conditions for strict anaerobiosis and to obtain surface colonies of obligate A. on an ordinary Petri dish. Using this method, one can obtain isolates from an isolated colony with the same ease and convenience as under aerobic conditions, which allowed the purification of some mixed anaerobic isolates that were previously considered pure. MacIntosh and Fields constructed an apparatus in the form of a hermetically sealing jar, in which a capsule with palladium asbestos is placed. Hydrogen is passed through the heated capsule, which ignites and burns until all the oxygen is consumed. Substances possessing reducing properties (sodium formate, indigo carmine, glucose, ammonium sulfide, etc.) are usually added to nutrient media for culturing A.