Methanol oxidation in a spontaneous mutant ofThiosphaera pantotrophawith a methanol-positive phenotype is catalysed by a dye-linked ethanol dehydrogenase

A spontaneous Thiosphaera pantotropha mutant (Tp9002) that is able to grow on methanol has been isolated. With hybridization experiments it has been demonstrated that mxaF, the gene encoding the large subunit of methanol dehydrogenase, is absent from T. pantotropha. In Tp9002, a dye-linked enzyme activity was found with a substrate specificity similar to that of the dye-linked ethanol dehydrogenase from Pseudomonas aeruginosa. The N-terminus of a 26-kDa cytochrome c, exclusively synthesized in Tp9002, is homologous to the N-terminus of the electron acceptor of ethanol dehydrogenase. These results suggest that in Tp9002 a dye-linked ethanol dehydrogenase is responsible for methanol oxidation, using a 26-kDa cytochrome c as electron acceptor.