ARE RUMINAL BACTERIA ARMED WITH BACTERIOCINS

The production of toxic compounds or antibiotics is a common component of intermicrobial competitive interactions, and many of these toxins have been adopted and adapted for the control of microbial populations . One class of these toxins, the bacteriocins, is a heterogeneous grou p of proteinaceous antibiotics that often display a high degree of tar get specificity, although many have a very wide spectrum of activity. To date, only limited information is available concerning the occurren ce of bacteriocins among ruminal isolates or the sensitivity of rumina l microorganisms to exogenous bacteriocins. A survey of 50 strains of Butyrivibrio spp. isolated from a variety of sources (sheep, deer, and cattle) for bacteriocin production indicated a high incidence of bact eriocin-like activity (50%). Many of these inhibitory compounds appear to have a broad spectrum of activity, which suggests that bacteriocin s may have a significant impact on both the competitive fitness of ind ividual microbial strains within the rumen and on the overall structur e of the microbial population within the rumen. Selected bacteriocins from lactic acid bacteria also were shown to have activity against But yrivibrio spp. and may have application in ruminant systems. Bacterioc ins may provide an alternative group of antibiotics for the manipulati on of ruminal microbial populations. Bacteriocins have significant adv antages over other antibiotics in target specificity, susceptibility t o proteolytic digestion, possibility of genetic transfer and manipulat ion, and, in the case of some bacteriocins derived from lactic acid ba cteria, a long history of safe use.