Clostridium herbivorans sp. nov., a cellulolytic anaerobe from the pig intestine.

A new cellulolytic anaerobic clostridium was isolated from the intestinal tract of pigs. The single isolate was a gram-positive, motile rod, formed terminal to subterminal swollen sporangia, and required a fermentable carbohydrate for growth. Cellulose, cellobiose, maltose, starch, and glycogen supported growth, but glucose and fructose did not. The major end products from the fermentation of cellobiose were butyrate and formate; minor amounts of hydrogen and ethanol were also formed. Ruminal fluid (15%) or yeast extract (1%) was required for good growth. The optimum temperature for growth was 39 to 42 degrees C, and the optimum pH was 6.8 to 7.2. Cell lysis occurred rapidly once stationary growth was reached. A 16S rRNA sequence analysis showed that the strain was related to a group of gram-positive anaerobes that includes Clostridium oroticum and the cellulolytic species Clostridium polysaccharolyticum and Clostridium populeti. The DNA base composition of the isolate is 38 mol% G + C. We propose the name Clostridium herbivorans for this organism; strain 54408 (= ATCC 49925) is the type strain.