Dechloromonas aquae sp. nov., A Novel Species Isolated from Aquaculture Water of Grass Carp.

A novel bacterial strain, designated Dechloromonas aquae ZY10, was isolated from the aquaculture water of grass carp. The colonies exhibited diameters ranging from approximately 1 to 3 mm and were characterized by a creamy-white coloration, circular shape, smooth texture, translucency, and a convex profile. The cells were facultatively anaerobic and motile, utilizing a single polar flagellum for movement. They were rod-shaped, reproduced through binary fission, and were identified as Gram-negative, oxidase-negative, and catalase-positive. Optimal growth was observed between 37 and 40 °C, within a pH range of 7.0-9.0, and at a NaCl concentration of 0% (w/v). The respiratory quinone was ubiquinone-8 (97.6%) and ubiquinone-7 (2.4%), and the major polar lipids were phosphatidylethanolamine (PE), aminophospholipid (APL), diphosphatidylglycerol (DPG), and phosphatidylglycerol (PG). Phylogenetic analysis based on 16S rRNA gene sequences suggested that ZY10 formed a lineage within the genus Dechloromonas and showed the highest 16S rRNA gene sequence similarity to "D. hankyongensis" XY25 (96.5%), followed by D. denitrificans ED1 (96.4%), D. hortensis MA-1 (96.1%) and D. agitata CKB (96.0%) and Azonexus. caeni Slo-05 (95.5%). The predominant fatty acids of ZY10 were summed feature 3 (comprising C ω6c and/or C ω7c) and C. The whole genome of ZY10 was 3,568,927 bp in size, including 3,275 protein-coding genes, 72 tRNA genes, and 15 rRNA genes, and the genomic DNA G + C content was 62.0 mol%. The orthologous average nucleotide identity, average amino acid identity, and digital DNA-DNA hybridization values between ZY10 and other species within the family Azonexaceae were 78.0-81.5%, 71.8-73.9%, and 20.3-23.0%, respectively. Therefore, based on phenotypic, chemotaxonomic, and phylogenetic analyses, the isolated ZY10 (= MCCC 1K08699 = KCTC 72749) is proposed as type strain of the novel species Dechloromonas aquae sp. nov.