Enzymes were assayed by routine methods [3‐5] in the extracts of cells grown on methanol or glucose. Autotrophic growth was studied in an H 2 : CO 2 : O 2 (75 : 15 : 10) atmosphere. The vitamin requirements of the strain was determined by growing it on methanol in a medium containing various vitamins (Sigma) at concentrations of 20 µ g/l instead of yeast extract. As can be seen from the table, A. tetraedrale possesses a complete set of enzymes necessary for the oxidation of methanol to CO 2 (the dehydrogenases of methanol, formaldehyde, and formate). The high activity of formaldehyde and formate dehydrogenases in the presence of NAD + indicates that the first step of oxidation of e 1 -substrates produces reduced pyridine nucleotides. The absence of serine‐glyoxylate aminotransferase and 3-hexulose-6-phosphate synthase suggests that the serine and ribulose monophosphate pathways are not involved in e 1 -metabolism. The higher activity of hydroxypyruvate reductase in glucose-grown cells may indicate that this enzyme is not involved in methanol metabolism. The high activity of phosphoribulokinase and ribulose 1,5-bisphosphate carboxylase shows that methanol is assimilated at the level of CO 2 via the ribulose bisphosphate (RuBP) cycle. Transketolase and transaldolase are shown to be involved in the conversion of glyceraldehyde-3-phosphate to xylulose-5phosphate, resulting in the regeneration of the primary CO 2 acceptor ribulose-1,5-bisphosphate. The cells grown on methanol or glucose were found to contain glycerate kinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, fructose-1,6-bisphosphate aldolase, 2-keto-3-deoxy-6-phosphogluconate aldolase, and 6-phosphofructokinase (ATP). Therefore, carbohydrates in this bacterium are metabolized via the glycolytic, pentose phosphate, and the Entner‐ Doudoroff pathways. The cells grown on glucose contained active glucokinase (ATP), pyruvate dehydrogenase, citrate synthase, 2-oxoglutarate dehydrogenase, isocitrate dehydrogenase (NADP + ), and malate dehydrogenase. The decreased activity of some enzymes of the tricarboxylic acid (TCA) cycle in the methanolgrown cells suggests that the role of this cycle in methylotrophs is predominantly biosynthetic. The activities of the key enzymes of the glyoxylate cycle (isocitrate lyase and malate synthase) in the methanol-grown cells were also lower than in the glucose-grown cells. was assimilated with the involvement of glycine dehydrogenase (NADPH), glutamate dehydrogenase (NAD(P)H), and the glutamate cycle enzymes glutamate synthase and glutamine synthetase. The anaplerotic fixation of CO 2 required pyruvate carboxylase, PEP carboxylase, and PEP carboxykinase. The activity of PEP carboxylase was higher during the methylotrophic growth of the bacterium. Thus, A. tetraedrale assimilates methanol by oxidizing it to CO 2 via formaldehyde and formate, followed by the fixation of the CO 2 in the RuBP pathway. Hence, this bacterium may be considered a facultative autotroph with elements of methylotrophic metabolism. This suggestion is confirmed by the ability of A. tetraedrale to grow in an atmosphere of CO 2 + H 2 + O 2 . The growth of this bacterium was found to be stimulated by biotin. The key enzymes of the autotrophic fixation of CO 2 (phosphoribulokinase and ribulose bisphosphate carboxylase) were induced during bacterial growth on methanol.