Polyphasic and phylogenomic reevaluation of Zhongshania and Marortus with the description of Zhongshania aquatica sp. nov.

Abstract

Advancing our understanding of microbial diversity and taxonomy in Korean coast, this study focuses on two intriguing bacterial genera, Marortus and Zhongshania, revealing significant insights through morphological and genomic analyses. The type strain, BJYM1T (= KCTC 92326T = NBRC 115677T) was isolated from seawater in Tongyeong, South Korea. BJYM1T was characterized as a Gram-negative aerobic strain with a rod shape and a single polar flagellum. Optimal growth conditions for BJYM1T were identified as 30 °C, pH 6.5, and 0-2% (w/v) NaCl on MA medium. Based on 16S rRNA gene sequence analysis, strain BJYM1T formed a clade with Z. aquimaris CAU 1632T, followed by M. luteolus ZX-21T and Z. marina DSW25-10T. The phylogenetic relationships of these four strains were also confirmed by genome-based and MALDI-TOF analyses. Strains Z. marina DSW25-10T, Z. aquimaris CAU 1632T, and BJYM1T possessed a single polar flagellum. The genome of strain BJYM1T had a size of 4.5 Mb with a DNA G + C content of 48.2 mol%. The major respiratory quinone was ubiquinone-8 (Q-8). Major polar lipids included phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and diphosphatidylglycerol (DPG). The major fatty acid was C16:0. Digital DNA-DNA hybridization values between reference strains were notably lower than 70%, with ANI values ？？ranging from 73.31 to 78.57% and AAI values ？？ranging from 75.91 to 83.01%. However, Z. marina DSW25-10T and M. luteolus ZX-21T exhibited dDDH values greater than 70%, as well as ANI and AAI values exceeding 95%. KEGG analysis revealed distinct metabolic pathways between two groups: Group 1 (Z. antarctica DSM 25701T, Z. aliphaticivorans SM-2T) had high cytochrome c oxidase and transporter: phosphonate pathway activities, while Group 2 (Z. marina DSW25-10T, Z. aquimaris CAU 1632T, M. luteolus ZX-21T, BJYM1T) exhibited Sec-SRP, chemotaxis, sulfide oxidation, and sulfur assimilation. BJYM1T displayed unique pathways, including the Cobalt transporter CorA, starch/glycogen synthesis, starch/glycogen degradation, and ferrous iron transporter FeoB. Through comprehensive physiological, phenotypic, and phylogenetic analyses, strain BJYM1T was identified as a new species within the genus Zhongshania, named Zhongshania aquatica sp. nov.