Proposal of Solimonas aquatica sp. nov., reclassification of Sinobacter flavus Zhou et al. 2008 as Solimonas flava comb. nov. and Singularimonas variicoloris Friedrich and Lipski 2008 as Solimonas variicoloris comb. nov. and emended descriptions of the genus Solimonas and its type species Solimonas soli

Abstract

A bacterial strain designated NAA16(T) was isolated from a freshwater spring in Taiwan and was characterized using a polyphasic taxonomic approach. Strain NAA16(T) was aerobic, Gram-staining-negative, rod-shaped, non-spore-forming and motile by means of a single polar flagellum. Growth occurred at 20-40 °C (optimum, 25 °C), at pH 7.0-8.0 (optimum, pH 7.5) and with up to 1 % NaCl (optimum, 0.5 %). Phylogenetic analyses based on 16S rRNA gene sequences showed that the closest relatives of strain NAA16(T) were Singularimonas variicoloris MN28(T), Sinobacter flavus CW-KD 4(T) and Solimonas soli DCY12(T), with respective sequence similarities of 96.7, 96.6 and 96.2 %. Phylogenetic trees reconstructed from 16S rRNA gene or rpoB sequences (encoding the β-subunit of the RNA polymerase) revealed that the novel strain NAA16(T) and these three closest relatives formed an independent phylogenetic clade within the Gammaproteobacteria. Strain NAA16(T) contained C₁₆:₀, C₁₈:₁ω7c and summed feature 3 (C₁₆:₁ω7c and/or C₁₆:₁ω6c) as predominant fatty acids and possessed phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an uncharacterized aminophospholipid as dominant polar lipids. The major isoprenoid quinone was Q-8. The DNA G+C content of strain NAA16(T) was 66.2 mol%. The taxonomic relationship of strain NAA16(T), Singularimonas variicoloris DSM 15731(T), Sinobacter flavus DSM 18980(T) and Solimonas soli LMG 24014(T) was clarified by means of a direct experimental comparison. Based on phenotypic, chemotaxonomic and phylogenetic data, the descriptions of the genus Solimonas and its type species Solimonas soli are emended. Members of the genus are Gram-negative, oxidase- and catalase-positive, aerobic or facultatively anaerobic and chemo-organotrophic. Chemotaxonomically, members of the genus Solimonas possess Q-8 as the major respiratory quinone, C₁₆:₀ and C₁₈:₁ω7c as predominant fatty acids and phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an uncharacterized aminophospholipid as dominant polar lipids; the DNA G+C content is 64.9-68.4 mol%. Phylogenetic evidence, supported by chemotaxonomic and phenotypic data, allowed us to assign strain NAA16(T) to the genus Solimonas within the novel species Solimonas aquatica sp. nov. (type strain NAA16(T) = BCRC 17835(T) = LMG 24500(T)). The reclassification of Sinobacter flavus as Solimonas flava comb. nov. (type strain CW-KD 4(T) = DSM 18980(T) = KCTC 12881(T) = CCTCC AB 206145(T)) and Singularimonas variicoloris as Solimonas variicoloris comb. nov. (type strain MN28(T) = DSM 15731(T) = LMG 22844(T)) is also proposed.