[Classification of Methylomonas rubra sp. nov]

Strain Methylomonas rubra 15sh(T), deposited in several collections of microorganisms (NCIMB 11913(T) = UCM B-3075(T) = ACM 3303(T)), is the subject of numerous studies. However, the name of this strain is not valid, primarily due to the phenotypic similarity of the species M. rubra to the species M. methanica. The results of the present study and data available in the literature indicate that M. rubra deserves the status of a separate species. Strains of M. rubra differ from strains of M. methanica in a number of properties, such as the ability to reduce nitrates to nitrites, the structure of intracytoplasmic membranes, and the presence of a new coenzyme Q. The distinctions between the species M. rubra and M. methanica were confirmed by comparison of electrophoretic patterns of their cellular proteins, by results of DNA-DNA hybridization, and by the data from 16S rRNA gene sequencing (the level of phylogenetic homology between these two species was below 95%). Phylogenetic and phenotypic analyses showed that strains of M. rubra cannot be assigned to any species of the genus Methylomonas. Results of polyphasic analysis suggest an independent taxonomic status of strain Methylomonas rubra 15sh(T). This paper contains description of Methylomonas rubra sp. nov. with the type strain 15sh(T) = NCIMB 11913T = UCM B-3075(T) = ACM 3303(T). The nucleotide sequence of the 16S rRNA gene of strain 15sh(T) has been deposited with the GenBank database under the accession number AY995198.