台灣地熱區 Silanimonas-like 新穎嗜熱性蛋白細菌之研究

Abstract

Six pale yellow-pigmented organisms with optimal growth temperature around 50 oC, were isolated from hot springs in Taiwan. These strains were motile with single polar flagellum, non-spore forming, alkaliphilic, gram-negative rods. The G+C contents (mol %) of these isolates were ranged from 68.7 to 73.3. Phylogenetic analysis of the 16S rDNA and physiological, biochemical studies showed that these isolated can be classified into two groups. Group Ⅰ including isolates NTU-1000, NTU-1555 and NTU-1310 showed 99.6 % to 99.8 % sequences similarity to Silanimonas lenta 25-4T. All these strains can hydrolyze starch. The pH range for growth was 7.0-12.0, with an optimal at pH 9.0. Strains NTU-1000, NTU-1310, NTU-1555 and S. lenta 25-4T can grow in nutrient broth containing 1 % NaCl. Fructose was utilized by strains of Group Ⅰ and Silanimonas lenta 25-4T. NTU-1000, NTU-1310, NTU-1555 and S. lenta 25-4T produced the following enzymes: alkaline phosphatase; esterase(C4); esteraselipase(C8); lipase(C14); leucine arylamidase; trypsin; a-chymotypsin; acid phosphatase; Naphthol-AS-BI-phosphohydrolase. Group Ⅱ including isolates NTU-1133, NTU-1197 and NTU-1358 showed 94.8 % to 95.0 % sequences similarity to S. lenta 25-4T. Different from S. lenta 25-4T that hydrolysis of starch was not observed by these strains. Isolates NTU-1133 and NTU-1197 could grow in nutrient broth containing 2 % NaCl, however NTU-1358 and S. lenta 25-4T could grow at salt concentrations up to 3 %. Strain NTU-1133 and S. lenta 25-4T could assimilate cellobiose and D-glucose, however NTU-1197, NTU-1358 could not. Strain NTU-1197 could utilize mannitol; strain NTU-1133 could utilize raffinose and trehalose, but S. lenta 25-4T could not use these carbohydrates. Strains NTU-1133, NTU-1197, NTU-1358 and S. lenta 25-4T produced the following enzymes: alkaline phosphatase; esterase (C4); esteraselipase (C8); leucine arylamidas; trypsin; a-chymotypsin; acid phosphatase; Naphthol-AS-BI-phosphohydrolase. Differences in the characteristics of the strains were as follows: valine arylamidase and cystine arylamidase were positive in NTU-1133, NTU-1197, NTU1358 and a-glucosidase in NTU-1358. The major cellular fatty acids of NTU-1133, NTU-1197 and NTU1358 were 15:0 iso, 16:0 iso and 17:0 iso. 16:0 fatty acids were detected in the strains of Group Ⅱ but not in S. lenta 25-4T. Based on the DNA-DNA hybridization (low than 70 %) and the divergence in 16S rDNA (higher than 3 %). These three isolates (NTU-1133, NTU-1197, NTU1358) could be considered as new species of Silanimonas.