The anti-quorum sensing activity and bioactive substance of a marine derived Streptomyces

Since bacterial quorum sensing system has been verified to regulate many microbial physiological activities, such as virulence factor production and biofilm formation in pathogens, blocking quorum sensing has being recognized as a viable approach for the development of novel therapeutics in treating bacterial infections. In this study, quorum quenching activities of marine actinomycetes isolated from seawater sample were investigated. Out of 56 morphological different strains, 5 strains had been found exhibiting anti-quorum sensing activity against the violacein production of Chromobacterium violaceum 12472. One highly active strain HY026 was identified as Streptomyces parvulus based on the 16S rDNA sequence analysis and morphological features. Spent culture medium of HY026 could also significantly inhibit the biofilm formation of four bacteria. One major active compound named F1-4, accounting for 26.3% of crude extracts, was obtained from HY026 cultures and identified as actinomycin D based on the analysis of the NMR and MS. F1-4 could significantly inhibit the violacein production of C. violaceum with the inhibition rate of 64.9% but not affect the bacterial growth at the concentration of 12.5 mu g/mL. F1-4 could also inhibit the prodigiosin production of Serratia proteamaculans 657 with the pigment inhibition zone of 13.5mm at concentration of 25 mu g/disc without affecting the bacterial growth. Another pure compound, cyclic (4-hydroxy-Pro-Phe) was also isolated and identified from this actinomycetes strain. The higher production and easier isolation of actinomycin D from S. parvulus HY026 indicated that this strain could be a potential source of quorum sensing inhibitors.