Effects of ammonia and amino acids on the growth and proteolytic activity of three species of rumen bacteria:: Prevotella albensis, Butyrivibrio fibrisolvens, and Streptococcus bovis

The addition of increasing physiological concentrations of ammonia or amino acids had distinct effects on the growth and proteolytic activity of Streptococcus bovis JB1, Prevotella albensis, and Butyrivibrio fibrisolvens DSM3071. The growth of S. bovis and B. fibrisolvens was enhanced by NH3 and AA, and that of P. albensis was reduced compared with a control with protein as the sole source of nitrogen. The proteolytic activity of S. bovis and P. albensis was reduced, but that of B. fibrisolvens was improved. NH3 seemed to act mainly on the cell-associated fraction of the proteolytic activity, while the action of AA was not specific. In the rumen the proteolytic activity of S. bovis and P. albensis would be optimal at low concentrations of NH3 or AA (<0.05 and <0.27 g/L respectively). In contrast, B. fibrisolvens would need higher concentrations (0.5 g/L of NH3 or 2.7 g/L of AA). It can be assumed that these bacteria will grow in different ecological niches.