Study on antibacterial activity of sponge-associated marine bacterium Pseudoalteromonas sp. NJ6-3-1 induced by diketopiperazines

Abstract

The objective was to isolate a sponge assocd. marine bacterium Pseudoalteromonas piscicida NJ6-3-1 with remarkable biol. activities, and to investigate whether its antibacterial metabolites were regulated and induced by quorum sensing autoinducer mols. We studied the relationship between the antibacterial activity and bacterial d. by changing the growth condition of bacterium NJ6-3-1. Results demonstrated that it had the quorum sensing mechanism in NJ6-3-1. To use three kinds of diketopiperazines of the metabolites of NJ6-3-1 as autoinducer mols., we monitored the antibacterial activity of marine bacterium NJ6-3-1 with low cell d. when the species were co-cultured with these three kinds of diketopiperazines. The results demonstrated that there was a close correlation between antibacterial activity and cell d., and there was quorum sensing mechanism in NJ6-3-1. The marine bacterium NJ6-3-1 could produce antibacterial compds. only on the high cell d. (OD630>0.4), and don't produce antibacterial compds. on the lower cell d. conditions, which were as follow: 1/5MB and 25°C. The results also demonstrated that cyclo(L-Phe-L-Val) existing in the metabolites of NJ6-3-1 could induce the prodn. of antibacterial substance from marine bacteria NJ6-3-1 even under low cell d. conditions below the required threshold value. The results, as described above, provided preliminary evidence for supporting the hypothesis that the antibacterial activity of NJ6-3-1 was controlled by the quorum sensing system of interspecies fashions, and its antibacterial activity was controlled by autoinducer mol. of cyclo(L-Phe- L-Val). [on SciFinder(R)]