Diversity of extracellular proteolytic activities among Prevotella species from the rumen

The current research was aimed at comparing proteolytic activities among ruminal Prevotella spp. Growth rates of Prevotella sp. 2202, Prevotella ruminicola D31d, P. brevis GA33, P. albensis M384, and P. bryantii B₁4 varied with N source, and no one N source produced the fastest growth in all species. Proteolytic activity was greatest with casein compared with peptides, AA, and NH₄Cl in all species. Proteolytic activity of Prevotella sp. 2202, P. brevis GA33, and P. bryantii B₁4 was modulated by N source. With gelatin co-polymerized SDS-PAGE, the extracellular activities of the Prevotella spp. showed wide variation in number, size, and type of proteases. Prevotella sp. 2202 and P. albensis M384 produced metalloproteases of low molecular weight (40 kDa). P. ruminicola D31d produced one cysteine protease (100-200 kDa) and two metalloproteases (90-100 kDa). P. brevis GA33 generated a diffuse clearing zone (95-160 kDa) containing serine, cysteine, and metalloproteases. P. bryantii B₁4 produced a metalloprotease greater that 200 kDa in size. The molecular sizes provided are estimations and served only to differentiate among the bacterial species in this study. Large variations in proteolytic activities among species and the known genetic diversity of the Prevotella taxon suggested that targeting this bacterial assemblage for genetic manipulation in order to alter the bacterial impact on ruminal protein degradation would be difficult.