Phylogenetic diversity and biological activities of marine actinomycetes isolated from sediments of the Yellow Sea Cold Water Mass, China

Abstract

In China's Yellow Sea Cold Water Mass (YSCWM), the unique environmental conditions (e.g. low temperature, high salinity and large temperature gradient) may support the growth of novel microbial populations with specific biological activities. In this study, 172 isolates of marine actinomycetes were obtained from 20 sediment samples of the YSCWM. Based on phylogenetic analysis of 16S rRNA genes, the actinomycete isolates were classified into five actinobacterial taxa. Members of Streptomyces were widely dominant (63.3%) while those of Nocardiopsis, Actinoalloteichus, Micromonospora and a novel genus Spinactinospora accounted for smaller proportions (19.1%, 8.7%, 7.6% and 1.2%, respectively). Of the 172 actinomycete isolates, 33.7% exhibited antibacterial activity against at least one of the four human pathogens tested (Bacillus subtilis, Escherichia coli, Staphylococcus aureus and Edwardsiella tarda), whereas 65.1–93.6% were capable of producing exoenzymes (lipase, caseinase and amylase). The largest number, highest diversity and greatest antibacterial rate of the actinomycetes were obtained with three culture media containing starch, aspartate and peptone, and glycerol and arginine, respectively. The isolates associated with antibacterial activity and/or exoenzyme production are potential sources for discovering industrially useful molecules/enzymes. Our results provide new insights into the phylogenetic diversity, antimicrobial activity, and enzyme production capability of marine actinomycetes in the YSCWM, expanding the scope for finding industrially important actinomycetes.