Microbial growth on C1 compounds. Uptake of [14C]formaldehyde and [14C]formate by methane-grown Pseudomonas methanica and determination of the hexose labelling pattern after brief incubation with [14C]methanol

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Abstract
A study has been made of the incorporation of carbon from [C14] formaldehyde and [C14]formate by cultures of P. methanica growing on methane. The distribution of radioactivity within the nonvolatile constituents of the ethanol-soluble fractions of the cells, after incubation with labelled compounds for periods of up to 1 min., has been analysed by chromatography and radioautography. Radioactivity was fixed from [C14]formaldehyde mainly into the phosphates of the sugars, glucose, fructose, sedoheptulose and allulose. Very little radioactivity was fixed from [C14]formate; after 1 min. the only products identified were serine and malate. The distribution of radioactivity within the carbon skeleton of glucose, obtained from short-term incubations with [C14]methanol of P. methanica growing on methane, has been investigated. At the earliest time of sampling over 70% of the radioactivity was located in C-1; as the time increased the radioactivity spread throughout the molecule. The results have been interpreted in terms of a variant of the pentose phosphate cycle, involving the condensation of formaldehyde with C-l of ribose 5-phosphate to give allulose phosphate.