Asticcacaulis aquaticus sp. nov., Asticcacaulis currens sp. nov. and Asticcacaulis machinosus sp. nov., isolated from streams in PR China.

Abstract

Three Gram-stain-negative, aerobic, rod-shaped, stalked and motile strains with a polar flagellum (BYS171WT, DXS10WT and LKC15WT) were isolated from streams in PR China. Comparisons based on 16S rRNA gene sequences showed that strains BYS171WT and DXS10WT had the highest 16S rRNA gene sequence similarities (98.1 and 98.6 %, respectively) to Asticcacaulis excentricus CB 48T, and strain LKC15WT showed 99.6 % similarity to Asticcacaulis endophyticus ZFGT-14T. These three strains showed 16S rRNA gene sequence similarities of less than 96.9 % to other species of the genus Asticcacaulis. A phylogenetic tree reconstructed based on 16S rRNA gene sequences also showed that strains BYS171WT and DXS10WT took A. excentricus CB 48T as their closest neighbour, and strain LKC15WT formed a tight cluster with A. endophyticus ZFGT-14T. The phylogenomic tree also showed that these three strains belong to the genus Asticcacaulis and form a distinct clade with the species of the genus Asticcacaulis. The major cellular fatty acids of these three strains were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C16 : 0 and 11-methyl C18 : 1 ω7c. Their polar lipids mainly consisted of phosphatidylglycerol, unidentified glycolipids and nitrogen-containing phosphoglycolipids. The calculated OrthoANIu and digital DNA-DNA hybridization values among strains BYS171WT, DXS10WT, LKC15WT and other related strains were less than 87.2 % and 34.0 %, respectively, indicating that these three strains should represent three independent novel species of the genus Asticcacaulis, for which the names Asticcacaulis aquaticus sp. nov. (type strain BYS171WT=GDMCC 1.3226T=KCTC 92612T), Asticcacaulis currens sp. nov. (type strain DXS10WT=GDMCC 1.3224T=KCTC 92543T) and Asticcacaulis machinosus sp. nov. (type strain LKC15WT=GDMCC 1.3225T=KCTC 92544T) are proposed.