Synergistic antimicrobial activity of metabolites produced by a nonobligate bacterial predator.

A naturally occurring, gram-negative, nonobligate predator bacterial strain 679-2, exhibits broad-spectrum antimicrobial activity that is due, in part, to the production of three extracellular compounds. Antimicrobial-activity-directed fractionation of a culture of strain 679-2 against a panel of microorganisms has led to the isolation of three compounds: pyrrolnitrin, maculosin, and a new compound, which we have named banegasine. Although pyrrolnitrin is well known in the literature, it has not been found in cells with the herbicide maculosin. Further, this is the first report of production of maculosin by a prokaryote. Both maculosin and banegasine, which displayed no antimicrobial activities alone, were found to potentiate the antimicrobial activity of pyrrolnitrin. Based on 16S rRNA sequence, cellular fatty acid composition, and biochemical and cultural characteristics, strain 679-2 appears to represent a new genus and species of eubacteria, Aristabacter necator. The potent, broad-spectrum antimicrobial activity of predator strain 679-2 may be due to synergism between metabolites.