MICROBIAL GROWTH ON C1 COMPOUNDS. SYNTHESIS OF CELL CONSTITUENTS BY METHANE- AND METHANOL-GROWN PSEUDOMONAS METHANICA.

1. A study has been made of the incorporation of carbon from [(14)C]methane, [(14)C]methanol and [(14)C]bicarbonate by cultures of Pseudomonas methanica growing on methane, and [(14)C]methanol by cultures of the same organism growing on methanol. 2. The distribution of radioactivity within the non-volatile constituents of the ethanol-soluble fractions of the cells, after incubation with labelled compound for periods up to 3min., has been analysed by chromatography and radioautography. 3. Over 90% of the radioactivity fixed from [(14)C]methane or [(14)C]methanol at the earliest times of sampling appeared in phosphorylated compounds. Glucose phosphate and fructose phosphate together constituted the largest part of the radioactive phosphates (70-90%); phosphoglycerate was a relatively minor component (2-17%). Other compounds becoming labelled during the incubation included glycine, serine, glutamate, aspartate, malate, citrate and alanine. 4. The first stable products of [(14)C]bicarbonate fixation were malate and aspartate (containing between them over 90% of the total radioactivity fixed at the earliest times of sampling). 5. The percentage of the total radioactivity fixed that was contained in each of the radioactive compounds has been plotted against time. The slopes of the curves obtained show that hexose phosphates are primary stable products of [(14)C]methane and [(14)C]methanol incorporation and that aspartate and malate are primary stable products of [(14)C]bicarbonate incorporation. 6. No carboxydismutase activity has been found in cell-free extracts of the organism. This fact, together with the other findings, shows that an autotrophic metabolism involving the ribulose diphosphate cycle of carbon dioxide fixation cannot be operating.