Pontibrevibacter nitratireducens gen. nov., sp. nov., a member of the family Rhodobacteraceae isolated from seawater of the Indian Ocean and intertidal zone

Abstract

Two Gram-stain-negative, facultatively anaerobic, non-motile, rod-shaped bacteria, strains h42^T and ALG8, were isolated individually from the Indian Ocean and intertidal zone of Zhoushan, China. The results of 16S rRNA gene sequence analysis showed that the sequence similarity between strains h42^T and ALG8 was 99.7 %, and the closest related strains were Monaibacterium marinum C7^T (97.77 and 97.62 %) and Pontivivens insulae GYSW-23^T (95.31 and 95.45 %). Phylogenetic analysis based on 16S rRNA gene sequences shows that these two novel strains belong to a distinct new lineage of the family Rhodobacteraceae in the order Rhodobacterales. The average nucleotide identity and in silico DNA-DNA hybridization values between the two novel strains and M. marinum C7^T and P. insulae GYSW-23^T were 72.73-78.15 % and 19.70-20.80 %, respectively. The DNA G+C content of strains h42^T and ALG8 was 62.36 % and 62.17 mol %. The major fatty acids (>10 %) in strain h42^T were C_{18 : 0}, C_{19 : 0} cyclo ω8c and summed feature 8 (C_{18 : 1} ω6c and/or C_{18 : 1} ω7c), and in strain ALG8 were C_{19 : 0} cyclo ω8c and summed feature 8 (C_{18 : 1}ω6c and/or C_{18 : 1} ω7c). The predominant isoprenoid ubiquinone of the two novel strains was Q-10; their major polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, two unidentified glycolipids, an unidentified aminoglycolipid, an unidentified phospholipid and an unidentified lipid. Based on the results of the morphological, physiological, chemotaxonomic and phylogenetic analysis of these two strains, a novel species of a new genus in the family Rhodobacteraceae is proposed, named as Pontibrevibacter nitratireducens gen. nov., sp. nov. The type strain and non-type strain of P. nitratireducens are h42^T (=KCTC 72875^T=CGMCC 1.17849^T=MCCC 1K04735^T) and ALG8 (=KCTC 82194=MCCC 1K04733).

Keywords: Pontibrevibacter nitratireducens; Rhodobacteraceae; offshore; open sea; phylogenetic analysis.