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

Abstract

The incorporation of C from [C14] methane, [C14] methanol and [C14] bicarbonate by cultures of P. methanica growing on methane, and [C14] methanol by cultures of the same organism growing on methanol was studied. Over 90% of the radioactivity fixed from [C14] methane or [C14] methanol appeared initially in phosphorylated compounds. Glucose phosphate and fructose phosphate 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. The first stable products of [C14] bicarbonate fixation were malate and aspartate (containing over 90% of the total radioactivity). The percentage of the total radioactivity fixed that was contained in each of the radioactive compounds was plotted against time. The slopes of the curves show that hexose phosphates are primary stable products of [C14] methane and [C14] methanol incorporation and aspartate and malate are primary stable products of [C14] bicarbonate incorporation. There was no carboxydismutase activity in cell-free extracts of the organism. This indicates that an autotrophic metabolism involving the ribulose diphosphate cycle of CO2 fixation is not involved.