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 �XC (optimum, 25 �XC), 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 �]-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 C??:?, C??:?�s7c and summed feature 3 (C??:?�s7c and/or C??:?�s6c) 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, C??:? and C??:?�s7c 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.