Robiginitalea rubriflava sp. nov. and Robiginitalea insularis sp. nov., isolated from coastal seawaters of the Yellow Sea.

Abstract

Two Gram-stain-negative, aerobic, non-motile, rod-shaped bacterial strains, designated IMCC43444T and IMCC44478T, were isolated from surface seawater collected off Deokjeok Island and Jangbong Island, respectively, in the Yellow Sea. The two strains shared 100% 16S rRNA gene sequence similarity with each other but exhibited ≤ 96.2% similarity to validly published species of the genus Robiginitalea. Complete whole-genome sequences of IMCC43444T and IMCC44478T were 3.21 Mb and 3.30 Mb in size, with DNA G + C contents of 46.5% and 46.4%, respectively. Genome-based relatedness analyses revealed average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of 90.7% and 42.9% between the two strains, which are well below the accepted species-level thresholds. Furthermore, ANI (≤ 70.2%) and dDDH (≤ 17.8%) values relative to type strains of Robiginitalea species supported the conclusion that strains IMCC43444T and IMCC44478T each represent novel species within the genus. Chemotaxonomic characterization showed that iso-C15:0, iso-C17:0 3-OH and iso-C15:1 G were the major fatty acids of both strains; menaquinone-6 (MK-6) was the sole isoprenoid quinone; and the major polar lipids comprised phosphatidylethanolamine, glycolipids, aminolipids, phospholipids, and other unidentified lipids. Based on phylogenetic, genomic, and phenotypic evidence, strains IMCC43444T and IMCC44478T are proposed as two novel species, Robiginitalea rubriflava sp. nov. and Robiginitalea insularis sp. nov., respectively. The type strains are IMCC43444T (= KCTC 102397T = JCM 37893T) and IMCC44478T (= KCTC 102398T = JCM 37894T).