A Gram-negative, aerobic, coccobacillus to rod-shaped bacterium was isolated from three patients with chronic granulomatous disease. The organism was subjected to a polyphasic taxonomic study. A multilocus phylogenetic analysis based on the 16S rRNA gene, the internal transcribed spacer (ITS) region and the RecA protein demonstrated that the organism belongs to a new sublineage within the acetic acid bacteria in the family Acetobacteraceae. Phenotypic features are summarized as follows: the organism grew at an optimum temperature of 35-37 degrees C and optimum pH of 5.0-6.5. It produced a yellow pigment, oxidized lactate and acetate, the latter weakly, produced little acetic acid from ethanol and could use methanol as a sole carbon source. The two major fatty acids were a straight-chain unsaturated acid (C18:1omega7c) and C16:0. The DNA base composition was 59.1 mol% G+C. The very weak production of acetic acid from ethanol, the ability to use methanol, the yellow pigmentation and high optimum temperature for growth distinguished this organism from other acetic acid bacteria. The unique phylogenetic and phenotypic characteristics suggest that the bacterium should be classified within a separate genus, for which the name Granulibacter bethesdensis gen. nov., sp. nov. is proposed. The type strain is CGDNIH1T (=ATCC BAA-1260T=DSM 17861T).