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Isolation and Characterization of Several Cellulolytic Bacteria from In Vitro Rumen Fermentations¹

Department of Animal Science, Ohio Agricultural Experiment Station, Wooster

ABSTRACT

Twenty-five strains of cellulolytic bacteria were isolated from in vitro fermentations carried out with mixed cultures of rumen bacteria. Based on morphology, five of these strains were selected for further study and their individual characteristics are reported. All five strains were anaerobic, nonmotile, and cellulolytic. Two of the strains were Gram-negative rod-shaped bacteria belonging to the species Bacteroides succinogenes Hungate. The three remaining strains were Gram-variable cocci, placed in the species Ruminococous flavefaciens Sijpesteijn. These bacteria, isolated from a 24-hr in vitro mixed culture, were thus true representatives of ruminal cellulolytic bacteria. Two of the isolated organisms had slightly different nutritional requirements than reported for previously isolated strains. One strain of B. succinogenes appeared to have an absolute requirement for one or more amino acids, since no growth was observed, even after incubation for one month, when casein hydrolysate was omitted from the defined medium. The other difference observed was with one strain of R. flavefaciens. This organism grew well, after an extended lagphase, on a purified medium devoid of volatile fatty acids. However, when casein hydrolysate was omitted from this medium no growth was observed.

¹ Approved for publication as Journal Article No. 103-62 by the Associate Director of the Ohio Agricultural Experiment Station.