KREBS CYCLE FUNCTION IS REQUIRED FOR ACTIVATION OF THE SPOOA TRANSCRIPTION FACTOR IN BACILLUS-SUBTILIS

Expression of genes early during sporulation in Bacillus subtilis requ ires the activity of the transcription factor encoded by spo0A. The ac tive, phosphorylated form of Spo0A is produced through the action of a multicomponent pathway, the phosphorelay. A mutant defective in the f irst three enzymes of the Krebs citric acid cycle was unable to expres s early sporulation genes, apparently because of a failure to activate the phosphorelay. Cells that produce an altered Spo0A protein that ca n be phosphorylated by an alternative pathway mere not dependent on Kr ebs cycle function for early sporulation gene expression. These findin gs suggest that Krebs cycle enzymes transmit a signal to activate the phosphorelay and that B. subtilis monitors its metabolic potential bef ore committing itself to spore formation.