Methanol assimilation and disaimilation pathways and ammonia assimilntion pathway were investigated in four obligate methanol-utilizing bacteria through the detection of key enzymes. Both hexulose phoephate syntheteae and hexulose phosphate isomerase, key enzymes of the ribulose monophosphate pathway (RE') for methnnol assimilation were detected whereas four key enzymes (hydroxy pyruvate reductase, Locitrate lyase, malyl-CoA-lyase and glyoxylate aminotransferase) that are characteristic of the serine assimilation pathway were absent. Key enzymes for the two methanol dissimilation pathwap, the linear sequence enzymes formaldehyde and formate dehydrogenase and the RMP cyclic sequence enzymes glucose-6-phosphate dehydrogenase and 6-phosphate gluconate dehydrogenase were all detected. Ammonia was assimilated via the glutamate dehydrogenase pathway and not vin the glutamine synthetase and glutamate synthase pathway.