Vullapa Arunpairojana

Diversity of marine gliding bacteria in Thailand and their cytotoxicity

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.

Bensingtonia thailandica sp. nov., a novel basidiomycetous yeast species isolated from plant leaves in Thailand

Ten strains which were characterized by the formation of ballistoconidia, the absence of xylose in whole-cell hydrolysates, the presence of Q-9 as the major ubiquinone isoprenologue, the inability to ferment sugars and positive diazonium blue B and urease reactions were isolated from plant samples collected in Thailand. These isolates were closely related to Bensingtonia phyllada based on the analysis of 18S rDNA sequences. On the basis of the morphological, physiological and chemotaxonomic properties, the 10 isolates were assigned to the genus Bensingtonia. DNA complementarity showed that these isolates were genetically distinct from known species of the genus Bensingtonia. The isolates are described as Bensingtonia thailandica sp. nov. The type strain is strain TY-138T (= JCM 10651T).

Control of the plant pathogenic fungus Macrophomina phaseolina in mung bean by a microalgal extract

An anti‐fungal antibiotic was characterized from an extract of Calothrix sp. TISTR 8906 with respect to an inhibition effect on plant pathogenic fungi. Optimal medium for anti‐fungal compound production was modified from nitrogen‐free BGA medium by the addition of NaN03 at the concentration of 1.5gL‐1, increasing K2HP04 concentration to 1.5 g L‐1 and decreasing NaCl concentration to 0.03 g L‐1 with an initial pH of 7.0. Algal growth, anti‐fungal activity and anti‐fungal compound production could be increased 2.6‐fold, four‐fold and 10‐fold, respectively. Crude algal extract formulated with surfactant applied to Macrophomina phaseolina at a concentration of 250 μg seed‐1 showed the same efficiency at inhibition as the commercial fungicide, mancozeb, at the recommended dose of 200 μg seed‐1, both in laboratory and pot experiments.

Kockovaella barringtoniae sp. nov., a new basidiomycetous yeast species isolated from a plant leaf collected in a tropical rain forest in Thailand

One yeast strain characterized by the proliferation of non-ballistosporous stalked conidia, budding cells and ballistoconidia, the presence of xylose in whole-cell hydrolysates, the presence of Q-10 as the major ubiquinone isoprenologue, the inability to ferment sugars and positive diazonium blue B (DBB) and urease reactions was isolated from a plant sample collected in a tropical rain forest in Thailand. The isolate clustered with Kockovaella species in the 18S rDNA-based tree. On the basis of the morphological, biochemical and molecular phylogenetic characteristics, the isolate was assigned to the genus Kockovaella. DNA complementarity experiments showed that the isolate was genetically distinct from known species of the genus Kockovaella. The isolate is described as Kockovaella barringtoniae sp. nov. The type strain is strain TY-278T (= JCM 10998T = TISTR 5770T).