Taxonomic identification of a novel strain of Streptomyces cavourensis subsp. washingtonensis, ACMA006, exhibiting antitumor and antibacteria activity.

Taxonomically diverse and genetically specialized, marine microorganisms have great potential in generating bioactive substances. A previous study isolated a novel actinomycete strain designated ACMA006 and revealed that the fermentation broth of ACMA006 (FBA6) significantly inhibited the growth of a series of tumor cell lines. The present study examined various characteristics of the ACMA006 strain, including its morphological, physiological, and biochemical nature, and the 16S rDNA gene sequence of ACMA006 and biological activity of FBA6. The ACMA006 strain grew at an optimal temperature of 28°C on nearly all media tested, except for Czapek's agar, producing an exuberant substrate and aerial hyphae. Phylogenetic analysis showed that the 16S rDNA gene sequence of ACMA006 was closely related to that of Streptomyces cavourensis subsp. washingtonensis, with a sequence similarity of nearly 100%. However, ACMA006 differed somewhat from Streptomyces cavourensis subsp. washingtonensis in terms of its morphological, physiological, and biochemical characteristics. According to a bioactivity assay, FBA6 strongly inhibited the growth of hepatocellular carcinoma cell line HepG2, while it was weakly cytotoxic to human normal hepatocytes LO2 according to an MTT assay. In addition, the growth of bacterial strains Bacillus subtilis and Staphylococcus aureus but not Escherichia coli, B. aerogenes, Pseudomonas fluorescence, and B. proteus was significantly suppressed by FBA6 as indicated by the filter paper disc method. Results of this study indicated that the strain ACMA006 represents a new strain of the Streptomyces cavourensis subsp. washingtonensis and that the active metabolites of this strain are candidates for utilization as anticancer or antibacterial agents.