Marine bacteria carrying nonribosomal peptide synthetase (NRPS) genes could be a promising source of anticancer compounds. This study evaluated the anticancer activity of sponge-associated bacteria with diverse NRPS genes. Nine isolates used in this study possessed diverse NRPS genes, as detected by polymerase chain reaction (PCR) screening. 16S rRNA-based identification exhibited that all nine isolates belonged to the family of Gammaproteobacteria class and were of the genus Pseudoalteromonas, Pseudomonas, or Serratia. Enterobacterial repetitive intergenic consensus- PCR confirmed that all isolates were different strains. Ethyl acetate extracts of the nine bacteria showed toxicity against Artemia salina and median lethal concentration (LC50) values of 30.94–179.41 μg/ml. Of the three bacterial isolates with the lowest LC50, the STIL 37-derived extract showed the highest anticancer activity and a high selectivity index against three cancer cell lines (A549, MCF-7, and WiDr) with median inhibition concentration values of 163.26– 304.51 μg/ml, but there was no effect on human mammary epithelial cells (MCF-12A), as tested by microculture tetrazolium test. According to gas chromatography-mass spectrometry analysis, hexadecanoic acid was found to be the most dominant compound in STIL 37 extract. In conclusion, all nine strains of sponge-associated bacteria, especially STIL 37, could potentially be used in the development of new anticancer drugs.
Key words: Cytotoxicity, Nonribosomal peptide synthetase (NRPS) gene, Sponge-associated bacteria, 16S-rRNA
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