Flectobacillus longus sp. nov. and Flectobacillus rivi sp. nov., isolated from streams in China and reclassification of Flectobacillus rhizosphaerae as a synonym of Flectobacillus roseus.

Abstract

Three Gram-stain-negative, aerobic, rod-shaped, non-motile strains (LYT7WT, DC10W and LFS242WT) were isolated from streams in PR China. Comparisons based on the 16S rRNA gene sequences showed that these three strains showed high 16S rRNA gene sequence similarity to Flectobacillus roseus GFA-11T (99.2, 98.8 and 99.8 %, respectively) and Flectobacillus rhizosphaerae JC289T (98.8, 98.6 and 99.4 %, respectively), and less than 96.6 % to other species of the genus Flectobacillus. The phylogenetic tree reconstructed based on the 16S rRNA gene sequences showed that strains LYT7WT, DC10W, LFS242WT, F. roseus GFA-11T and F. rhizosphaerae JC289T formed a tight cluster. The phylogenomic tree also supported the above robust phylogenetic relationships. The calculated OrthoANIu and digital DNA-DNA hybridization values between strains LYT7WT and DC10W were 95.2 % and 61.9 %, respectively. Although these values are located in the transition region for species demarcation, the similar physiological and genotypic characteristics supported that strains LYT7WT and DC10W should belong to the same species. The pairwise OrthoANIu and digital DNA-DNA hybridization values between strain LFS242WT and its related strains were less than 91.8 and 45.3 %, respectively, indicating that strain LFS242WT should represent an independent novel species of the genus Flectobacillus. It should be noticed that the pairwise OrthoANIu and digital DNA-DNA hybridization values between strains F. roseus LMG 24501T and F. rhizosphaerae KCTC 42575T were 96.9 and 73.1 %, respectively. The similar physiological and genotypic characteristics also supported that F. rhizosphaerae Ramaprasad et al. 2015 should be a synonym of F. roseus Sheu et al. 2009. Combining the above descriptions, strains LYT7WT, DC10W and LFS242WT should represent two novel species of the genus Flectobacillus, for which the names Flectobacillus longus sp. nov. (type strain LYT7WT=GDMCC 1.3222T=KCTC 92561T) and Flectobacillus rivi sp. nov. (type strain LFS242WT=GDMCC 1.3223T=KCTC 92562T) are proposed.