Characteristics of a new cellulolytic Clostridium sp. isolated from pig intestinal tract

Gram-positive, spore-forming, motile, cellulolytic rods were isolated from 10(7) dilutions of pig fecal samples. The pigs had previously been fed pure cultures of the ruminal cellulolytic organism Clostridium longisporum. Isolates formed terminal to subterminal spores, and a fermentable carbohydrate was required for growth. Besides cellulose, the isolates utilized cellobiose, glycogen, maltose, and starch. However, glucose, fructose, sucrose, pectin, and xylose were not used as energy sources. Major fermentation products included formate and butyrate. The isolates did not digest proteins from gelatin or milk. Unlike C. longisporum, which has limited ability to degrade cell wall components from grasses (switchgrass, bromegrass, and ryegrass), the swine isolates were equally effective in degrading these components from both alfalfa and grasses. The extent of degradation was equal to or better than that observed with the predominant ruminal cellulolytic organisms. On the basis of morphology, motility, spore formation, fermentation products, and the ability to hydrolyze cellulose, the isolates are considered to be a new species of the genus Clostridium. It is unclear whether C. longisporum played a role in the establishment or occurrence of this newly described cellulolytic species. This is the first report of a cellulolytic Clostridium sp. isolated from the pig intestinal tract.