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Research Article

Schlegelella aquatica sp. nov., a novel thermophilic bacterium isolated from a hot spring

Chou, Yi-Ju, Sheu, Shih-Yi, Sheu, Der-Shyan, Wang, Jih-Terng, Chen, Wen-Ming

International Journal of Systematic and Evolutionary Microbiology 2006; 56(12):2793 · https://doi.org/10.1099/ijs.0.64446-0

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Summary auto-generated

Researchers isolated a moderately thermophilic bacterium from a hot spring in Taiwan and characterized it using polyphasic taxonomy. The strain, designated wcf1T, is a Gram-negative, rod-shaped, motile bacterium that grows optimally at 50°C and pH 7.0. Phylogenetic analysis of 16S rRNA gene sequences showed the isolate was most closely related to Schlegelella thermodepolymerans (97.8% similarity), but DNA-DNA hybridization revealed only 45% relatedness, indicating it represents a distinct species. The strain differs from S. thermodepolymerans in cellular fatty acid composition, G+C content (69.2 mol% versus 70.0 mol%), and various biochemical characteristics including nitrate reduction, carbon substrate assimilation patterns, and antibiotic susceptibilities. The organism was isolated from the natural habitat of a hot spring rather than the man-made environments where S. thermodepolymerans strains have been found. Based on comprehensive genotypic and phenotypic data, the authors propose the name Schlegelella aquatica sp. nov. for this novel thermophilic bacterium.

Key findings

  • Schlegelella aquatica sp. nov. is a novel moderately thermophilic bacterium isolated from a natural hot spring in Taiwan
  • The strain shows 97.8% 16S rRNA similarity to S. thermodepolymerans but only 45% DNA-DNA hybridization relatedness, confirming species-level distinction
  • S. aquatica differs from S. thermodepolymerans in fatty acid composition, G+C content, and biochemical characteristics including nitrate reduction and substrate assimilation patterns
  • The isolate grows optimally at 50°C and pH 7.0 and is susceptible to multiple antibiotics including ampicillin, chloramphenicol, and tetracycline

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Abstract

A moderately thermophilic bacterial strain designated wcf1T, isolated from a hot spring located in the Tainan area, southern Taiwan, was characterized using a polyphasic approach. The cells were Gram-negative, non-pigmented, rod-shaped, non-spore-forming and motile. Phylogenetic analysis using 16S rRNA gene sequences showed that the strain formed a monophyletic branch towards the periphery of the evolutionary radiation occupied by the genus Schlegelella; its only close neighbour was the type strain of Schlegelella thermodepolymerans, K14T (97.8 %). The isolate was clearly distinguishable from other strains using phylogenetic analysis, DNADNA hybridization, fatty acid composition data and a range of physiological and biochemical characteristics. It was evident from the genotypic and phenotypic data that strain wcf1T represents a novel species in the genus Schlegelella, for which the name Schlegelella aquatica sp. nov. is proposed, with the type strain wcf1T (=BCRC 17557T=LMG 23380T).