Diversity of marine gliding bacteria in Thailand and their cytotoxicity

Abstract

HeLa: cervical cancer HT-29: colon cancer KB: oral cancer MCF-7: breast adenocarcinoma PCR: polymerase chain reaction SK: skim milk medium SRB: sulphorodamine B 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 *Corresponding author 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.

Evaluating methods for the isolation of marine-derived fungal strains and production of bioactive secondary metabolites

“…When considering the culture media used for the isolation and purification of marine-derived fungal strains, we observed a large variation in the number of strains obtained, depending on the media used for such purpose (Figure 2), in agreement with Bredholt et al (2008) for the isolation of Streptomycetes and Sangnoi et al (2009) for the isolation of marine gliding bacteria. The use of artificial sea water (ASW) as a growth medium provided bioactive crude extracts.…”

“…Over 84% of the strains isolated displayed antibiotic activity against at least one human microbial pathogen, and over 23% inhibited at least four of such pathogenic strains. Sangnoi et al (2009) also used a single medium for the isolation of 84 strains of marine gliding bacteria from biofilms, invertebrates and algae. Among the strains isolated, 27 were selected based on their morphological features for growth in four different media for the production of extracts.…”