Studies on Anaerobic Bacteria

Abstract

III. An extensive review is given of the literature relating to the 3 groups of heat resistant thermophilic spoilage organisms in non- or semi-acid canned foods. These are (1) flat sour organisms, characterized by acid production without gas from carbohydrates, (2) gas-forming (non H2S) organisms, which by virtue of gas (CO2 and H2) production cause "hard swells" in canned foods, and (3) sulfid or "sulfur stinker" organisms, characterized by non-saccharo-lytic and feebly proteolytic properties. A detailed study is reported of the technique of culture developed for the second group (thermophilic anaerobes). Liver infusion (liquid infusion sterilized over dried particles of extracted tissue) is recommended for enrichment and general cultivation purposes in preference to others tested. Vegetable extract infusion agar (dilution of canned strained peas, spinach, etc.) was successfully used as a plating medium. Tryptone broth was most satisfactory as a base medium for physiological studies. Details of test tube and plate technique (involving the use of unglazed porcelain plates in anaerobic jars) are given. Surface growth was obtained only with spore inocula. Methods for spore production and for maintenance of stock cultures are discussed.[long dash]IV. With the methods of culture described in a previous paper the taxonomic characteristics of 27 strains of thermophilic anaerobes were given. 7 of these had been isolated from sugar or "blown" cans of vegetables and 20 from enrichment cultures of soil from an asparagus field. 6 of the cultures were purified by single cell technique; 21 were subjected to serial single colony isolation. All the strains were long, slender, granulated bacilli bearing a round, strictly terminal spore. The cultures were Gram-negative and possessed peritrichiate flagella. Surface colonies were greyish-white and of medium size with rough, indistinct "feather" edges, often showing a slightly raised center. The cultures were strictly anaerobic and thermophilic temps. were preferable for growth. No proteolytic action was exhibited but saccharolytic properties were extensive though well defined. The monosaccharides, disaccharides and the glucosides tested were all fermented in contrast to the action on the alcohols, calcium lactate, and cellulose. Of the polysaccharides, inulin and pectin were not fermented but dextrin, glycogen and corn starch were utilized. There was no reduction of nitrates or production of H2S or indol. The cultures were non-pathogenic to rats and rabbits. Agglutinin production was successful. Review of the literature failed to reveal a similar organism, and the name Clostridium thermosaccharolyticum (p.200) is suggested.