Carbonatibacter coralli gen. nov., sp. nov., a carbonate-producing and vitamin B12-sharing bacterium isolated from coral Porites lutea, reclassification of Kiloniellaceae and proposal of Aestuariispiraceae fam. nov.

A Gram-stain-negative, non-spore-forming, carbonate-producing, vitamin B₁₂-sharing, aerobic rod, designated strain GXU_MW_B19^T, was isolated from coral <i>Porites lutea</i>. Cells grew at 20-40 °C, pH 6.5-10 and no more than 5% NaCl (w/v). Global alignment based on 16S rRNA gene sequence indicated that the new isolate is most close to members of the genus <i>Kiloniella</i> with identities of 92.9-94.1%, while sharing no more than 91.7% similarity with other type strains. The maximum average nucleotide identity and average amino acid identity to closely related species were 69.5 and 62.8%, respectively. Phylogenetic analysis based on both 16S rRNA gene sequences and the whole-genome sequences indicated that strain GXU_MW_B19^T forms a stable cluster with genus <i>Kiloniella</i> in the order <i>Rhodospirillales</i>. The genome G+C content was 54.5 mol%. The dominant cellular fatty acids (≥10%) included iso-C_{10 : 0}2OH, C_{12 : 1}, C_{14 : 1} ω5c and iso-C_{17 : 0}3OH. The major polar lipids comprised phosphatidylethanolamine, diphosphatidylglycerol, unidentified ninhydrin-positive lipid and three unidentified lipids. Alpha-1,6-glucosidase, alkaline phosphatase, isochorismate-related enzymes and P2-like prophage-related proteins were encoded in the new isolate, all of which were absent in closely related species. Based on these distinct phylogenetic, genomic and chemotaxonomic characteristics, the new isolate is suggested to represent a new species in a new genus, for which the name <i>Carbonatibacter coralli</i> gen. nov., sp. nov. is proposed. The type strain is GXU_MW_B19^T (=KCTC 8092^T=MCCC 1K08794^T). Finally, phylogenetic analyses led to the reclassification of the <i>Kiloniellaceae</i> and the proposal of ‌<i>Aestuariispiraceae‌</i> fam. nov.