Phylogenetic relationships of the genera Stella, Labrys and Angulomicrobium within the 'Alphaproteobacteria' and description of Angulomicrobium amanitiforme sp. nov.

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.