Methylobacterium hispanicum sp nov and Methylobacterium aquaticum sp nov., isolated from drinking water

Members of the genus Methylobacterium are ubiquitous in nature and can be isolated from almost any freshwater environment where dissolved oxygen exists. This genus is composed of a variety of pink-pigmented, facultatively methylotrophic (PPFM) bacteria. During a screening programme to monitor the bacterial population present in the drinking water of a municipal water supply in Seville (Spain) during the year 2003, five strains of PPFM bacteria were isolated and characterized. Analysis of their complete 16S rRNA gene sequences revealed that they constituted two separate phylogenetic groups (strains GP34(T) and GRII 8, and strains GR16(T), GP22 and GP32, respectively) showing highest similarity to members of the genus Methylobacterium. The highest 16S rRNA sequence similarities of strain GP34(T) were found with respect to the type strains of Methylobacterium radiotolerans (96.6%) and Methylobacterium fujisawaense (96.4%) and the highest 16S rRNA sequence similarities of strain GR16(T) were to the type strains of Methylobacterium extorquens (96.0%) and Methylobacterium rhodesianum (95.8%). The G+C content of their DNA ranged from 66.5 to 67.8 mol%. DNA-DNA hybridization studies confirmed that they constituted two separate genospecies. On the basis of this phenotypic, phylogenetic and genotypic study, two novel species of the genus Methylobacterium are proposed: Methylobacterium hispanicum sp. nov., with type strain GP34(T) (CECT5997(T) ( CM 7219(T)=DSM 16372(T) = CIP 108332(T)), and Methylobacterium aquaticum sp. ncv., with type strain GR16(T) (CECT 5998(T) = CCM 7218(T) = DSM 1637 (T) = CIP 108333(T)).