Antibacterial activity of sponge associated marine bacterium Pseudoalteromonas sp. NJ6-3-1 regulated by quorum sensing

OBJECTIVE: We chose a sponge-associated marine-bacterium Pseudoalteromonas piscicida NJ6-3-1 to study whether its antibacterial activity were regulated by quorum sensing. METHODS: We studied the relationship between the antibacterial activity and bacterial density under various growth conditions. To simulate the natural competitive environment, we monitored the antibacterial activity at low cell density when the species were co-cultured with Staphylococcus aureus. RESULTS: Antibacterial activity correlated closely with cell density. Marine bacterium NJ6-3-1 started producing antibacterial compounds when cell density reached the threshold value of OD(630) = 0.4. Some signal molecules existing in the metabolites of S. aureus could induce the production of antibacterial substance by marine-bacteria NJ6-3-1 even cell density below the required threshold. CONCLUSION: The results provide preliminary evidence to support the hypothesis that the antibacterial activity of NJ6-3-1 was regulated by the quorum sensing system of intraspecies and interspecies.