Antibiotic production by the marine photosynthetic bacterium Chromatium purpuratum NKPB 031704: localization of activity to the chromatophores

Over 200 strains of marine purple photosynthetic bacteria were isolated. Two strains showed antibiotic activity towards Saccharomyces cerevisiae and were tentatively identified as Chromatium purpuratum. Crude antibiotic, prepared by solvent extraction, showed a broad antimicrobial spectrum. The highest activity was found in the chromatophore fraction. Chromatographic separation of purified light harvesting complex from one strain, NKPB 031704, showed the presence of two separate pigmented compounds which were responsible for antimicrobial activity. Our findings reveal the unexpected ability of photosynthetic bacteria to produce broad spectrum antibiotics. In addition, this is the first example of intracellular localization of antibiotic activity in a marine bacterium.