Novel methylotrophy genes of Methylobacterium extorquens AM1 identified by using transposon mutagenesis including a putative dihydromethanopterin reductase

Ten novel methylotrophy genes of the facultative methylotroph Methylobacterium extorquens AMI were identified from a transposon mutagenesis screen. One of these genes encodes a product having identity with dihydrofolate reductase (DHFR). This mutant has a C-1-defective and methanol-sensitive phenotype that has previously only been observed for strains defective in tetrahydromethanopterin (H4MPT)-dependent formaldehyde oxidation. These results suggest that this gene, dmrA, may encode dihydromethanopterin reductase, an activity analogous to that of DHFR that is required for the final step of H4MPT biosynthesis.