Phylogeny by a polyphasic approach of the order Caulobacterales, proposal of Caulobacter mirabilis sp nov., Phenylobacterium haematophilum sp nov and Phenylobacterium conjunctum sp nov., and emendation of the genus Phenylobacterium

Three strains of Gram-negative, rod-shaped, non-spore-forming bacteria were isolated from fresh water and human blood. As determined by analyses of 16S rRNA gene sequences, the prosthecate strain FWC 38(T) was affiliated to the alphaproteobacterial genus Caulobacter, with Caulobacter henricii (96.8 %) and Caulobacter fusiformis (96.8 %) as its closest relatives. The non-prosthecate strain LMG 11050(T) and the prosthecate strain FWC 21(T) both belonged to the genus Phenylobacterium with Phenylobacterium koreense (96.9 %) and Phenylobacterium immobile (96.3 %) as the closest relatives. This affiliation was supported by chemotaxonomic data (polar lipids and cellular fatty acids). Physiological and biochemical tests allowed genotypic and phenotypic differentiation of the novel strains from all hitherto recognized species of the genera Caulobacter and Phenylobacterium. The strains therefore represent novel species, for which the names Caulobacter mirabilis sp. nov. (type strain FWC 38(T)=LMG 24261(T)= CCUG 55073(T)), Phenylobacterium conjunctum (type strain FWC 21(T) LMG 24262(T)= CCUG 55074(T)), the first described prosthecate Phenylobacterium species, and Phenylobacterium haematophilum sp. nov. (type strain LMG 11050(T)= CCUG 26751(T)) are proposed. Marker nucleotides within the 16S rRNA genes were determined for the genera Asticcacaulis, Brevundimonas, Caulobacter and Phenylobacterium and the description of the genus Phenylobacterium is emended.