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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 38T 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 11050T and the prosthecate strain FWC 21T 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 38T=LMG 24261T=CCUG 55073T), Phenylobacterium conjunctum (type strain FWC 21T=LMG 24262T=CCUG 55074T), the first described prosthecate Phenylobacterium species, and Phenylobacterium haematophilum sp. nov. (type strain LMG 11050T=CCUG 26751T) 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.

The unusually shaped bacteria of the genera Stella, Labrys and Angulomicrobium have been described based on their cell morphology and biochemistry. However, their phylogenetic relationships remain unresolved. An earlier study that was based on 5S rRNA gene sequences placed the genus Stella within the 'Alphaproteobacteria'. In the present report, polar lipids and 16S rRNA genes of the type strains of the two species in the genus Stella, Stella humosa DSM 5900(T) and Stella vacuolata DSM 5901(T), are studied, as well as the type strains of the monospecific genera Labrys (Labrys monachus VKM B-1479(T)) and Angulomicrobium (Angulomicrobium tetraedrale DSM 5895(T)). It was found that the genus Stella belongs to the order Rhodospirillales in the family Rhodospirillaceae, and not to the Acetobacteraceae. Whilst the position of the genus Angulomicrobium in the family Hyphomicrobiaceae was confirmed, the genus Labrys could not be placed into any known family, but was adjacent to the family 'Beijerinckiaceae'. In addition, data were obtained for strain VKM B-1336, which was shown not to belong to the genus Angulomicrobium, and strain NCIMB 1785(T) (=DSM 15561(T)), for which the name Angulomicrobium amanitiforme sp. nov. is proposed.

Five bacterial strains were isolated from a non-toxigenic strain of the marine dinoflagellate Alexandrium tamarense (Lebour) Balech CCMP 116 (NEPCC C116), during a survey of the diversity of bacteria associated with paralytic shellfish toxin-producing cultures of Alexandrium spp. (Dinophyta). All strains were strictly aerobic, Gram-negative, straight or curved rods. Cells were dimorphic, with stalks (or prosthecae) and non-motile or non-stalked and motile, by means of a single polar flagellum. The bacteria grew best at salt concentrations ranging from 2 to 10 % and growth occurred at 10 degrees C, but not at 50 degrees C. The G+C content of the chromosomal DNA of the strains was determined to be 61-62 mol%. Major cellular fatty acids of the bacteria presented a unique profile. 16S rRNA gene sequence analysis showed the five strains to be related to genera of budding bacteria of marine origin in the 'Alphaproteobacteria', namely, Hirschia, Maricaulis and Hyphomonas, although they exhibited substantial differences in morphology, substrate utilization and fatty acid profile to members of these genera. The five strains are proposed to comprise a new species of a new genus, Oceanicaulis alexandrii gen. nov., sp. nov., the type strain of which is C116-18(T) (=DSM 11625(T)=NCIMB 13905(T)).