ORIGINAL PAPER Isolation of marine bacteria with antimicrobial activities from cultured and field-collected soft corals Yu-Hsin Chen • Jimmy Kuo • Ping-Jung Sung • Yu-Chia Chang • Mei-Chin Lu • Tit-Yee Wong • Jong-Kang Liu • Ching-Feng Weng • Wen-Hung Twan • Fu-Wen Kuo Received: 6 March 2012 / Accepted: 20 July 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Bacteria associated with eight field-collected and five cultured soft corals of Briareum sp., Sinularia sp., Sarcophyton sp., Nephtheidae sp., and Lobophytum sp. were screened for their abilities in producing antimicrobial metabolites. Field-collected coral samples were collected from Nanwan Bay in southern Taiwan. Cultured corals were collected from the cultivating tank at National Museum of Marine Biology and Aquarium. A total of 1,526 and 1,138 culturable, heterotrophic bacteria were isolated from wild and cultured corals, respectively; sea- water requirement and antimicrobial activity were then assessed. There is no significant difference between the ratio of seawater-requiring bacteria on the wild and cul- tured corals. The ratio of antibiotic-producing bacteria within the seawater-requiring bacteria did not differ between the corals. Nineteen bacterial strains that showed high antimicrobial activity were selected for 16S rDNA sequencing. Three strains could be assigned at the family level (Rhodobacteraceae). The remaining 16 strains belong to eight genera: Marinobacterium (2 strains), Pseudoalte- romonas (1), Vibrio (5), Enterovibrio (1), Tateyamaria (1), Labrenzia (2), and Pseudovibrio (4). The crude extract from bacteria strains CGH2XX was found to have high cytotoxicity against the cancer cell line HL-60 (IC 50 = 0.94 lg/ml) and CCRF-CEM (IC 50 = 1.19 lg/ml). Our results demonstrate that the marine bacteria from corals have great potential in the discovery of useful medical molecules. Keywords Soft coral  Coral-associated bacteria  Antimicrobial activity  Cytotoxic activity  Obligate marine bacteria Introduction An increase of bacterial resistance to existing antibiotics has led to the search for new drugs, especially antibiotics. Bio- active compounds are traditionally screened from terrestrial microorganisms. However, the opportunity of finding novel antibiotics from terrestrial microorganisms has diminished (Hong et al. 2009a). The environments between oceanic and terrestrial systems are very different. As such, marine microorganisms may produce bioactive compounds not found in terrestrial habitats (Penesyan et al. 2009). It has been reported that marine invertebrates harbor a higher population of bacteria able to produce novel bioactive compounds (Burgess et al. 1999; Nithyanand et al. 2011). Previous studies on microbes associated with sponges have revealed Y.-H. Chen  P.-J. Sung  C.-F. Weng Graduate Institute of Biotechnology, National Dong Hwa University, Hualien 974, Taiwan Y.-H. Chen  J. Kuo  P.-J. Sung  Y.-C. Chang  M.-C. Lu Graduate Institute of Marine Biotechnology, National Dong Hwa University, Pingtung 944, Taiwan J. Kuo (&)  P.-J. Sung  M.-C. Lu  W.-H. Twan  F.-W. Kuo Department of Planning and Research, National Museum of Marine Biology and Aquarium, Pingtung 944, Taiwan e-mail: jimmy@nmmba.gov.tw T.-Y. Wong Department of Biology, University of Memphis, Memphis, TN 38152, USA J.-K. Liu Department of Biological Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan W.-H. Twan Department of Life Sciences, National Taitung University, Taitung 950, Taiwan 123 World J Microbiol Biotechnol DOI 10.1007/s11274-012-1138-7