Functionality of the xoxF gene in Methylobacterium dichloromethanicum DM4

Activation of expression of the xoxF gene encoding PQQ-dependent methanol/ethanol dehydrogenase (METDI2492) in dichloromethane (DCM)-grown Methylobacterium dichloromethanicum DM4 was first demonstrated. The sequence of the only XoxF homolog found in the genome of strain DM4 exhibited 50% identity to that of the protein (MxaF) of the large subunit of methanol dehydrogenase (MDH). A knock-out mutant with inactivated xoxF gene (ΔxoxF) was found to be unable to grow on methanol due to the absence of the expression of the gene cluster of the classical MDH, as was confirmed by the GFP test. When grown on succinate, the ΔxoxF mutant exhibited a lower growth rate on DCM than the original strain and was more sensitive to various stress factors (oxidative, osmotic, and heat shock). Based on these data, the xoxF gene was hypothesized to belong to a group of genes affecting the expression of proteins of general stress response.