Ruminococcin A, a new lantibiotic produced by a Ruminococcus gnavus strainisolated from human feces

When cultivated in the presence of trypsin, the Ruminococcus gnavus El stra in, isolated from a human fecal sample, was able to produce an antibacteria l substance that accumulated in the supernatant. This substance, called rum inococcin A, was purified to homogeneity by reverse-phase chromatography. I t was shown to be a 2,675-Da bacteriocin harboring a lanthionine structure. The utilization of Edman degradation and tandem mass spectrometry techniqu es, followed by DNA sequencing of part of the structural gene, allowed the identification of 21 amino acid residues. Similarity to other bacteriocins present in sequence libraries strongly suggested that ruminococcin A belong ed to class IIA of the lantibiotics. The purified ruminococcin A was active against various pathogenic clostridia and bacteria phylogenetically relate d to R. gnavus. This is the first report on the characterization of a bacte riocin produced by a strictly anaerobic bacterium from human fecal microbio ta.