綠島沿岸熱泉內 Marinobacter spp. 及 Hydrogenophilus sp. 新穎嗜熱菌之研究

Abstract

In this study, six strains of thermophilic halotolerant bacteria were isolated from geothermal areas in Lutao, Taiwan. They were NTU-445, NTU-1311, NTU-1438, NTU-1645, NTU-1689 and NTU-1701. After amplifying and sequencing the 16S rDNA of those strains , the sequences were compared on NCBI database. According to the 16S rDNA sequences, it is found that the strains might be classified into two groups : Genus Marinobacter and Genus Hydrogenophilus. Group I including isolated strains NTU-1645, NTU-1689 and NTU-1701, showed 96.5 % ~ 97.2 % 16S rDNA sequences similarity to Marinobacter lutaoensis BCRC 17087T, and 99.5 % ~ 99.7 % to each other. The optimal growth temperature of isolates was 50 oC. They were motile with single polar flagellum, non-spore forming gram-negative rods. The swarming motility of isolated strains is also more obvious than the type strain. The isolated strains could growth in medium containing 15 % NaCl, and utilitze citrate, D-cellulobiose, D-galactose, D-mannose, D-melibiose, D-raffinose, D-sobiotol, D-trehalose, D-xylose, glycerol, maltose, myo-inostiol, L-arginine, L-ornithine, L-valine as well as n-butanol as sole carbon source, while the type strain could not. Base on the DNA-DNA hybridization (lower than 70 %), the divergence in 16S rDNA (higher than 3 %), and some morphological, physiological, biochemical properties. The isolated strains could be considered as new species of Genus Marinobacter. Group II including isolated strains NTU-455, NTU-1311 and NTU-1438 showed 96.6 % ~ 97.3 % 16S rDNA sequences similarity to Hydrogenophilus thermoluteolus NBRC 14978T, and 99.1 % ~ 99.7 % to each other. The optimal growth temperature of strains was 50 oC. They were non-spore forming gram-negative rods. The isolated strains were motile with single polar flagellum, and the colonies of isolated strains were brown color. Those morphological properties were different from type strain. The isolated strains could grow in the medium containing 5 % NaCl and pH 9, and utilize D-fructose, D-galactose, D-melibiose, L-ramnose, L-proline, L-arginine and L-alanine as sole carbon source, but type strain can not. The isolated strains also produced the following enzymes: Alkaline phosphatase, Acid phosphatase and Naphthol-AS-BI-phosphohydrolase, and were Streptomycin-resistant. According to the DNA-DNA hybridization (lower than 70 %), the divergence in 16S rDNA (higher than 3 %), and above results, the isolated strains could be considered as new species of Genus Hydrogenophilus.