IDENTIFICATION OF PROTEOLYTIC RUMEN BACTERIA ISOLATED FROM NEW-ZEALAND CATTLE

The protease activities of 212 strains of rumen bacteria isolated from New Zealand cattle grazing pasture were measured. Thirty-seven per ce nt of strains had activity greater than or equal to the proteolytic ru men bacterium Prevotella ruminicola and 43 of these isolates were iden tified by morphology, carbon source utilization, Gram stain, biochemic al tests and fermentation end-product analysis. Hierarchical Cluster A nalysis showed that the strains formed four clusters: cluster A contai ned 26 strains and clustered with a reference strain of Streptococcus bovis; cluster C contained three strains and clustered with a referenc e strain of Butyrivibrio fibrisolvens, while clusters B (10 strains) a nd D (three strains) did not cluster with any of the remaining rumen b acterial type strains. Further tests identified strains of cluster B a s Eubacterium budayi, while cluster D strains most closely resembled B . fibrisolvens and were described as B. fibrisolvens-like. An uncluste red strain, C21a, was identified as P. ruminicola. The significance of these proteolytic bacterial populations is discussed in relation to p rotein breakdown in New Zealand ruminants.