Role of the spoT gene product and manganese ion in the metabolism of guanosine 5'-diphosphate 3'-diphosphate in Escherichia coli.

Addition of divalent ion chelating agents picolinic acid, 1,10-phenanthroline, or quinoline-2-carboxylic acid to wild type, relA, or relX, but not spoT strains of Escherichia coli increases the levels of guanosine 5'-diphosphate 3'-diphosphate (ppGpp). Poorly chelating analogs of these agents and a larger and more highly charged chelating agent, ethylene glycol bis(beta-amino-ethyl ether) N,N,N',N'-tetraacetic acid are ineffective. Mn2+ reverses the increase in ppGpp. The increase in ppGpp in wild type cells can be explained by an inhibition of degradation. In spoT cells the response is more complex; ppGpp does not increase although degradation is completely inhibited. The lack of increase in spoT cells suggests a role for spoT in synthesis of ppGpp in addition to its known role in degradation. Growth of both spoT+ and spoT cells is inhibited following chelator addition. This suggests that growth inhibition is through a mechanism not directly involving ppGpp. The results of this study provide evidence in intact cells for a role for Mn2+ and the spoT gene product in ppGpp degradation, and provide further evidence for an involvement of spoT and possibly divalent ions in ppGpp synthesis.