Enzymes of dimethylsulfone metabolism and the phylogenetic characterization of the facultative methylotrophs Arthrobacter sulfonivorans sp. nov., Arthrobacter methylotrophus sp. nov., and Hyphomicrobium sulfonivorans sp. nov.

Novel methylotrophic Arthrobacter and Hyphomicrobium species are described. Constitutive membrane-associated dimethylsulfone- and dimethylsulfoxide-reductases were found in Arthrobacter methylotrophus strain TGA and Hyphomicrobium sulfonivorans strain S1. Enzyme activities increased during growth with dimethylsulfone or dimethylsulfoxide, respectively, and different ratios of activity with different growth substrates indicated that they are separate enzymes. SDS-PAGE showed some membrane-associated polypeptides to be enhanced during growth with dimethylsulfone (54 kDa in H. sulfonivorans, 21-24 kDa, 54 kDa and 80 kDa in A. methylotrophus). Western blotting with anti-dimethylsulfoxide-reductase antibody showed cross-reaction with 54- and 21-kDa polypeptides in A. methylotrophus. All strains contained rhodanese and sulfur oxygenase after growth with dimethylsulfone. Sulfite was oxidized in the Arthrobacter species by APS reductase and sulfite dehydrogenase. H. sulfonivorans oxidized sulfite with APS reductase, which is unusual for an alpha-proteobacterium. The Arthrobacter species were distinguished from each other and from other Arthrobacter and Micrococcus species by 16S rRNA gene sequence analysis. The menaquinone and fatty acid profiles of the Arthrobacter species were similar. Their peptidoglycan structures were L-Lys- L-Ser- L-Thr- L-Ala for A. sulfonivorans and L-Lys- L-Ala(2-4) for A. methylotrophus. H. sulfonivorans exhibited gross morphology typical for Hyphomicrobium, but possessed helically twisted prosthecae. 16S rRNA gene sequence analysis showed it to be distinct from all the other Hyphomicrobium, Filomicrobium and Pedomicrobium species sequenced to date. Formal descriptions of the new species are given.