Rhodobacter amnigenus sp. nov. and Rhodobacter ruber sp. nov., isolated from freshwater habitats

Description of Rhodobacter flavimaris sp. nov. and proposal of the genera Paenirhodobacter, Sedimentimonas, and Sinirhodobacter as synonyms of Rhodobacter

Two Gram-stain-negative, aerobic, ovoid to short rod-shaped bacterial strains, designated as WL0062T and WL0115, were isolated from coastal zone of the Yellow Sea, Jiangsu Province, PR China, respectively. Strain WL0062T grew optimally at 28 °C, pH 7.0-8.0 and with 1.0-3.0% (w/v) NaCl. Strain WL0115 grew optimally at 28 °C, pH 6.0-7.0 and with 1.0-3.0% (w/v) NaCl. In the bac120 tree, strains WL0062T and WL0115 clustered together with Sedimentimonas flavescens B57T. The respiratory quinone of both strains was ubiquinone-10. The major polar lipids of both strains were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, glycolipid, phosphatidylmonomethylethanolamine, and one unidentified polar lipid. The major fatty acids of strain WL0062T were summed features 8 (C18 : 1  ω6c and/or C18 : 1  ω7c). The major fatty acids of strain WL0115 were summed features 8 (C18 : 1  ω6c and/or C18 : 1  ω7c), C18 : 0, iso-C17 : 1  ω5c and C20 : 4  ω6/9/12/15c (arachidonic acid). The G+C content of genomic DNA of strains WL0062T and WL0115 was 64.0 mol% in both of them. Combined with the analysis of average nucleotide identity, average amino acid identity, and digital DNA-DNA hybridization, strain WL0062T represents a novel species of the genus Rhodobacter, for which the name Rhodobacter flavimaris sp. nov is proposed. The type strain is WL0062T (=MCCC 1K06014T=JCM 34676T=GDMCC 1.2427T). Strain WL0115 (=MCCC 1K07531=JCM 35568=GDMCC 1.3088) should belong to the same species as Sedimentimonas flavescens B57T. In addition, on the basis of phylogenomic relationship and phenotypical characteristics, the genera Paenirhodobacter, Sedimentimonas, and Sinirhodobacter are proposed as synonyms of Rhodobacter.

Genome Sequence and Characterization of a Xanthorhodopsin-Containing, Aerobic Anoxygenic Phototrophic Rhodobacter Species, Isolated from Mesophilic Conditions at Yellowstone National Park

The genus Rhodobacter consists of purple nonsulfur photosynthetic alphaproteobacteria known for their diverse metabolic capabilities. Here, we report the genome sequence and initial characterization of a novel Rhodobacter species, strain M37P, isolated from Mushroom hot spring runoff in Yellowstone National Park at 37 °C. Genome-based analyses and initial growth characteristics helped to define the differentiating characteristics of this species and identified it as an aerobic anoxygenic phototroph (AAP). This is the first AAP identified in the genus Rhodobacter. Strain M37P has a pinkish-red pigmentation that is present under aerobic dark conditions but disappears under light incubation. Whole genome-based analysis and average nucleotide identity (ANI) comparison indicate that strain M37P belongs to a specific clade of recently identified species that are genetically and physiologically unique from other representative Rhodobacter species. The genome encodes a unique xanthorhodopsin, not found in any other Rhodobacter species, which may be responsible for the pinkish-red pigmentation. These analyses indicates that strain M37P is a unique species that is well-adapted to optimized growth in the Yellowstone hot spring runoff, for which we propose the name Rhodobacter calidifons sp. nov.