Diversity of marine gliding bacteria in Thailand and their cytotoxicity

 Yutthapong Sangnoi
Department of Industrial Biotechnology
Faculty of Agro-Industry
Prince of Songkla University
Hat Yai, Songkhla 90112, Thailand 

Pornpoj Srisukchayakul
Thailand Institute of Scientific and Technological Research
35 Moo 3, Technopolis, Khlong 5, Khlong Luang
Pathum Thani 12120, Thailand 

Vullapa Arunpairojana
Thailand Institute of Scientific and Technological Research
35 Moo 3, Technopolis, Khlong 5, Khlong Luang
Pathum Thani 12120, Thailand 

Akkharawit Kanjana-Opas*
Department of Industrial Biotechnology
Faculty of Agro-Industry
Prince of Songkla University
Hat Yai, Songkhla 90112, Thailand
Tel: 66 74286373
Fax: 66 74212889
E-mail: akkharawit.k@psu.ac.th

*Corresponding author

Financial support: Thailand Research Fund (MRG4880153) and a Biodiversity Research and Training Grant (BRTR_149011). Scholarship for YS from the Graduate School, Prince of Songkla University.

Keywords: Aureispira marina, Aureispira maritime, Fulvivirga kasyanovii, human cell lines, Rapidithrix thailandica, Tenacibaculum mesophilum.

Eighty-four marine gliding bacteria were isolated from specimens collected in the Gulf of Thailand and the Andaman Sea. All exhibited gliding motility and swarm colonies on cultivation plates and they were purified by subculturing and micromanipulator techniques. Their 16S rRNA genes were amplified by the polymerase chain reaction (PCR) technique. The phylogenetic analysis indicated that the represented isolates can be separated into six different clads (gr 1 - gr 6) within the Cytophaga-Flavobacterium-Bacteriodes (CFB) group. Group 1 formed a remote linear, with only 90% sequence similarity, from Flavobacteriaceae bacterium which indicated a potentially novel taxonomic group. Groups 2 and 3 were identified as the recently proposed Tenacibaculum mesophilum and Fulvivirga kasyanovii respectively. Groups 4, 5 and 6, consisting of the largest number of the members, were identified as Rapidithrix thailandica, Aureispira marina and Aureispira maritima respectively. The isolates were cultivated in four different cultivation media (Vy/2, RL 1, CY and SK) and the crude extracts were submitted to screen cytotoxicity using a sulphorodamine B (SRB) assay. The results from cytotoxic screening showed that groups 2, 4 and 6 were capable of producing the cytotoxic metabolites against selected human cell lines (breast adenocarcinoma (MCF-7), colon cancer (HT-29), cervical cancer (HeLa) and oral cancer (KB)). However, groups 1, 3 and 5 did not produce metabolites with cytotoxicity when cultivated in the same cultivation media as the previous groups. CY medium was the only cultivation medium which could yield the cytotoxic metabolites against MCF-7.