Bacteriocin-like activity of Butyrivibrio fibrisolvens JL5 and its effect on other ruminal bacteria and ammonia production.

When ruminal bacteria from a cow fed hay were serially diluted into an anaerobic medium that had only peptides and amino acids as energy sources, little growth or ammonia production was detected at dilutions greater than 10(-6). The 10(-8) and 10(-9) dilutions contained bacteria that fermented carbohydrates, and some of these bacteria inhibited Clostridium sticklandii SR, an obligate amino acid-fermenting bacterium. Phylogenetic analysis indicated that the most active isolate (JL5) was closely related to Butyrivibrio fibrisolvens B835. Strain JL5 inhibited B. fibrisolvens 49 and a variety of other gram-positive organisms, but it had little effect on most gram-negative ruminal bacteria. Strain JL5 did not produce a bacteriocin-like inhibitory substance (BLIS) until it reached the late log or stationary phase. The JL5 BLIS did not cause the lysis of B. fibrisolvens 49, but the intracellular potassium level, the ATP level, the electrical potential, and the viability decreased rapidly. The JL5 BLIS also caused marked decreases in the viability and cellular potassium level of C. sticklandii SR. The membrane potential and intracellular ATP level also declined. The BLIS was degraded very slowly by pronase E, but it could be precipitated with 60% ammonium sulfate and dialyzed (3,500-Da cutoff). The BLIS could be separated from other peptides by polyacrylamide gel electrophoresis, and C. sticklandii SR overlays indicated that the molecular size of this compound was approximately 3,600 Da. Based on these results, it appeared that the JL5 BLIS was a pore-forming peptide. Because carbohydrate-fermenting ruminal bacteria could inhibit the growth of obligate amino acid-fermenting bacteria, BLIS may play a role in regulating ammonia production in vivo.