Characterization of Rhodococcus wratislaviensis, a New Gram-Positive Facultative Methylotroph, and Properties of Its C1 Metabolism

Abstract

A facultative methylotroph, strain 2AzMo (VKM Ac-2782), was isolated from the coastal zone of the Sea of Azov. The cells of the isolate are aerobic gram-positive nonmotile rods. Optimal growth occurs at 1% NaCl, 28°C, and pH 7.5 with 1% СH3OH or 0.3% methylamine as the carbon and energy sources. A broad spectrum of polycarbon substrates is also utilized. Sequencing of the 16S rRNA gene of the strain revealed its similarity to Rhodococcus species: 99.9% to R. wratislaviensis IEGM 1112T (=NCIMB 13082T), 99.4% to R. imtechensis IEGM 940T (=RKJ300T), and 99.2% to R. koreensis IEGM 962T (=DNP505T). The level of DNA–DNA homology of strain 2AzMo with R. wratislaviensis IEGM 1112T (=NCIMB 13082T) was 76%, supporting its identification as a strain of this species. However, unlike strain 2AzMo, the type strain R. wratislaviensis IEGM 1112T, as well as other members of this genus (R. imtechensis IEGM 940T, R. koreensis IEGM 962T, and R. opacus IEGM 716T), do not grow on methanol and methylamine. Methanol oxidation by R.wratislaviensis 2AzMo is catalyzed by alcohol dehydrogenase, which uses 4-nitroso-N,N-dimethylaniline as an artificial electron acceptor. Methylamine is oxidized by methylamine dehydrogenase and the enzymes of the N-methylglutamate pathway. Formaldehyde is then assimilated via the fructose bisphosphate aldolase variant of the ribulose monophosphate pathway of C1 metabolism. Ammonium is assimilated by α-ketoglutarate reductive amination and via the glutamate cycle.