Analysis of two formaldehyde oxidation pathways in Methylobacillus flagellatus KT, a ribulose monophosphate cycle methylotroph

The roles of cyclic formaldehyde oxidation via B-phosphogluconate dehydroge nase and linear oxidation via the tetrahydromethanopterin (H4MPT)-linked pa thway were assessed in an obligate methylotroph, Methylobacillus flagellatu s KT. by cloning, sequencing and mutating two chromosomal regions containin g genes encoding enzymes specifically involved in these pathways: B-phospho gluconate dehydrogenase, glucose-6-phosphate dehydrogenase and methenyl H4M PT cyclohydrolase (gndA, zwf and mch). No null mutants were obtained in gnd A or zwf. implying that the cyclic oxidation of formaldehyde is Institute o f Genetics and required for C-1, metabolism in this obligate methylotroph, probably as the Selection of Industrial Micro-organisms, Ist main energy-ge nerating pathway, In contrast, null mutants were generated in proezd indica ting that the H4MPT-linked pathway is dispensable, These mutants showed enh anced sensitivity to formaldehyde, suggesting that this pathway plays a sec ondary physiological role in this methylotroph, This function is in contras t to Methylobacterium extorquens AM1. in which the H4MPT-linked pathway is essential.