Diversity and antibacterial activity of culturable actinobacteria isolated from five species of the South China Sea gorgonian corals

Abstract

This study describes the diversity and antibacterial activity of culturable actinobacteria isolated from five species of gorgonian corals (Echinogorgia aurantiaca, Melitodes squamata, Muricella flexuosa, Subergorgia suberosa, and Verrucella umbraculum) collected in shallow water of the South China Sea. A total of 123 actinobacterial isolates were recovered using ten different isolation media, and assigned to 11 genera, including Streptomyces and Micromonospora as the dominant genera, followed by Nocardia, Verrucosispora, Nocardiopsis, Rhodococcus, Pseudonocardia, Agrococcus, Saccharomonospora, Saccharopolyspora and Dietzia. Comparable analysis indicated that the numbers of actinobacterial genera and isolates from the five gorgonian coral species varied significantly. It was found that 72 isolates displayed antibacterial activity against at least one indicator bacterium, and the antibacterial strains isolated from different gorgonians had almost the same proportion (similar to 50 %). These results provide direct evidence for the hypotheses that gorgonian coral species contain large and diverse communities of actinobacteria, and suggest that many gorgonian-associated actinobacteria could produce some antibacterial agents to protect their hosts against pathogens. To our knowledge, this is the first report about the diversity of culturable actinobacteria isolated from gorgonian corals.The authors are grateful to the National Basic Research Program of China (Grant 2010CB833803), the Research Supported by the CAS/SAFEA International Partnership Program for Creative Research Teams (Grant KZCX2-YW-T001), the Knowledge Innovation Program of Chinese Academy of Science (Grant KSCX2-EW-G-12B), the National Science Foundation of China (Grant 40976090 and 41206139), National Key Technologies R&D Program (Grant 2011BAE06B04-03) and Guangdong Natural Science Foundation of China (Grant S2011040000144) for financial support. The authors are grateful to Dr. Hui Huang (South China Sea Institute of Oceanology, Chinese Academy of Sciences) for her kindness in identifying the gorgonian samples. And we are grateful to Hui Hou and Brandon Lalone for their help in language editing