Arenimonas subflava sp. nov., isolated from a drinking water network, and emended description of the genus Arenimonas , measured by two different methods (52.0 mol% and 55.9 mol%, respectively), was much lower than that of any member of the genus Arenimonas. The predominant fatty acids (.8 %) were iso-C 16:0 , iso-C 15:0 , iso-C 14:0 , iso-C 17:1 v9c and C 16:1 v7c alcohol. Strain PYM3-14T contained Q-8 as the major ubiquinone and phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and phosphatidylmonomethylethanolamine as the major polar lipids. According to phenotypic and genotypic data strain PYM3-14 T represents a novel species of the genus Arenimonas, for which the name Arenimonas subflava sp. nov. is proposed. The type strain is PYM3-14 T (5NCAIM B 02508 T 5DSM 25526 T ). On the basis of new data obtained in this study, an emended description of the genus Arenimonas is also proposed.The drinking water supply of Budapest (Hungary) is based on the River Danube's riverbank filtration wells. These wells provide consumers with excellent quality water, which needs only safety chlorination before consumption. Microbial communities of drinking water can change significantly in the collecting and chlorinated distributing pipelines from the wells to the consumers . From the collecting system of the drinking water network of Budapest many bacterial strains have been isolated and characterized taxonomically (Homonnay et al., 2008;Tó th et al., 2011;Makk et al., 2011).On the basis of 16S rRNA gene sequence analysis, a novel yellowish-white-pigmented isolate from the drinking water network of Budapest belonged to the class Gammaproteobacteria, and its closest relatives were species of the genus Arenimonas. The genus Arenimonas has the following characteristics: aerobic, Gram-stain-negative, non-sporeforming, rod-shaped bacteria with Q-8 as the major isoprenoid quinone. The predominant cellular fatty acids are iso-C 16:0 , iso-C 15:0 and iso-C 17:1 v9c. The genus was reported to be unable to reduce nitrate and nitrite (Kwon et al., 2007). At the time of writing, the genus includes seven species with validly published names. The type species of the genus is Arenimonas donghaensis which was isolated from seashore sand in Pohang city, South Korea Abbreviations: MALDI-TOF, matrix-assisted laser-desorption/ionization time-of-flight; meso-DAP, meso-diaminopimelic acid.