A novel arsenic-resistant bacterium, designated 42-50T, was isolated from the high-arsenic sediment of Jianghan Plain, Hubei Province, China. Phylogenetic and biochemical analysis indicated that this bacterium represents the first species of a novel genus belonging to the family Hyphomicrobiaceae. The 16S rRNA gene of strain 42-50T shares 96.3-94.2, 96.3, 96.2 and 94.9-93.8 % sequence identities to those of species from the genera Devosia, Youhaiella, Paradevosia and Pelagibacterium, respectively. The major cellular fatty acids are C16 : 0, C18 : 0, C18 : 1ω7c 11-methyl and summed feature 8 (comprising C18 : 1ω7c and C18 : 1ω6c). The predominant polar lipids are diphosphatidylglycerol, phosphatidylglycerol and two unidentified glycolipids. The predominant respiratory quinone is ubiquinone-10 (Q-10). The DNA G+C content of strain 42-50T is 73.7 mol%. The distinct phylogenetic lineage and unique cellular fatty acids suggest that strain 42-50T represents a novel species of a new genus affiliated with the family Hyphomicrobiaceae, for which the name Arsenicitalea aurantiaca gen. nov., sp. nov. is proposed. The type strain is 42-50T (=CCTCC AB 2014325T=KCTC 42825T).