Flectobacillus roseus sp. nov., isolated from freshwater in Taiwan

Abstract

Two Gram-negative, aerobic, pale pink/rose-coloured, rod-shaped, non-motile bacterial strains, designated GFA-11(T) and RG-4, were isolated from a freshwater fish culture pond and a freshwater spring sample, respectively. Based on characterization by using a polyphasic approach, the two strains showed highly similar phenotypic, physiological and genetic characteristics. They shared 99.9 % 16S rRNA gene sequence similarity and 89-94 % DNA-DNA relatedness, suggesting that they represent a single genomic species. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains GFA-11(T) and RG-4 formed a monophyletic branch at the periphery of the evolutionary radiation occupied by the genus Flectobacillus within the family Flexibacteraceae. Their closest neighbours were Flectobacillus major DSM 103(T) (97.7 % 16S rRNA gene sequence similarity) and Flectobacillus lacus CL-GP79(T) (95.9 %). Levels of DNA-DNA relatedness between the two novel strains and the type strains of F. major and F. lacus were less than 70 %. The results of physiological and biochemical tests allowed clear phenotypic differentiation of strains GFA-11(T) and RG-4 from recognized members of the genus Flectobacillus. The predominant fatty acid constituents of strain GFA-11(T) were C(16 : 1)omega5c (40.2 % of the total) and iso-C(15 : 0) (15.0 %). The DNA G+C content of strain GFA-11(T) was 39.7 mol%. On the basis of 16S rRNA gene sequence analysis and chemotaxonomic and physiological data, strains GFA-11(T) and RG-4 are considered to represent a novel species of the genus Flectobacillus, for which the name Flectobacillus roseus sp. nov. is proposed. The type strain is GFA-11(T) (=BCRC 17834(T)=LMG 24501(T)).