Methylibium petrolelphilum gen. nov., sp nov., a novel methyl tert-butyl ether-degrading methylotroph of the Betaproteobacteria

A Gram-negative, rod-shaped, motile, non-pigmented, facultative aerobe that grew optimally at pH 6(.)5 and 30 degrees C (strain PM1(T)) was isolated for its ability to completely degrade the gasoline additive methyl tert-butyl ether. Analysis of the 16S rRNA gene sequence indicated that this bacterium was a member of the class Betaproteobacteria in the Sphaerotilus-Leptothrix group. The 16S rRNA gene sequence identity to other genera in this group, Leptothrix, Aquabacterium, Roseateles, Sphaerotilus, Ideonella and Rubrivivax, ranged from 93 to 96%. The chemotaxonomic data including Q-8 as the major quinone, C16:1 omega 7c and C16: 0 as the major fatty acids and a DNA G+C content of 69 mol%, support the inclusion of strain PM1(T) in the class Betaproteobacteria. It differed from other members of the Sphaerotilus-Leptothrix group by being a facultative methylotroph that used methanol as a sole carbon source, and by also being able to grow heterotrophically in defined media containing ethanol, toluene, benzene, ethylbenzene and dihydroxybenzoates as sole carbon sources. On the basis of the morphological, physiological, biochemical and genetic information, a new genus and species, Methylibium petroleiphilum gen. nov., sp. nov., is proposed, with PM1(T) (= ATCC BAA- 1232(T)=LMG 22953(T)) as the type strain.