Abstract
A large, obligately anaerobic spirochete (strain PB) was isolated from bovine rumen fluid by a procedure involving rifampin as a selective agent. The helical cells measured 0.6 to 0.7 micron by 12 to 20 micron and possessed approximately 16 periplasmic flagella inserted near each end of the protoplasmic cylinder. The periplasmic flagella were arranged in a bundle wound around the cell body. Strain PB utilized as fermentable substrates various plant polysaccharides (e.g., pectin, arabinogalactan, starch, and inulin) as well as pentoses, hexoses, disaccharides, and uronic acids. Glucose was fermented to acetate, formate, and ethanol, whereas the fermentation of pectin or glucuronic acid yielded only acetate and formate as major end products. Determinations of radioactivity in end products and assays of enzymatic activities indicated that strain PB catabolized glucose via the Embden-Meyerhof pathway. Extracts of cells grown in pectin-containing media possessed relatively high levels of phospho-2-keto-3-deoxygluconate aldolase activity, an enzymatic activity typical of the Entner-Doudoroff pathway. The guanine-plus-cytosine content of the DNA of strain PB (54 mol%) was considerably higher than that of known host-associated anaerobic spirochetes. This study indicates that strain PB represents a new species of Treponema, for which we propose the name Treponema saccharophilum.