THE BIOLOGICAL CONTROL OF GLYCOGEN METABOLISM IN AGROBACTERIUM TUMEFACIENS

Abstract

The hypothesis has been advanced that the inhibition of phosphorylase by uridine diphosphate glucose (UDPG), together with the fact that the latter compound is the substrate for glycogen synthetase, is the basis of a mechanism for the biological control of glycogen metabolism in Agrobacterium tumefaciens. Experiments were designed to test this hypothesis on the assumption that such a control mechanism would manifest itself by the concentrations of UDPG and glycogen bearing some relationship to each other during various stages of growth and nutrition. Glycogen levels in the cells increased markedly during the lag phase of growth, decreased during the exponential growth phase, and increased again as growth ceased due to the depletion of nitrogen from the medium (nitrogen starvation). The UDPG concentration paralleled these changes, and a high positive correlation between the concentrations of UDPG and glycogen was demonstrated. The addition of ammonium chloride to nitrogen-starved cells caused a prompt resumption of growth, a sharp decrease in the UDPG concentration, and a somewhat smaller decrease in glycogen concentration. Cells placed in buffered salt solution and aerated had a low concentration of UDPG and exhibited a steady decline of the glycogen reserves. Although factors other than those considered here may also be of importance in the control of glycogen metabolism in this organism, the data in general support the hypothesis advanced above.