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 1112^T (=NCIMB 13082^T), 99.4% to R. imtechensis IEGM 940^T (=RKJ300^T), and 99.2% to R. koreensis IEGM 962^T (=DNP505^T). The level of DNA–DNA homology of strain 2AzMo with R. wratislaviensis IEGM 1112^T (=NCIMB 13082^T) was 76%, supporting its identification as a strain of this species. However, unlike strain 2AzMo, the type strain R. wratislaviensis IEGM 1112^T, as well as other members of this genus (R. imtechensis IEGM 940^T, R. koreensis IEGM 962^T, and R. opacus IEGM 716^T), 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.