Induction of sporulation in developmental mutants of Bacillus subtilis.

Abstract

Sporulation of the standard strain of Bacillus subtilis can be induced by decoyinine (a specific inhibitor of guanosine monophosphate synthesis) in the presence of excess ammonium ions, rapidly utilizable carbohydrates and phosphate. Certain developmental mutants unable to sporulate in usual sporulation media can also be induced to sporulate under these conditions. Among the inducible strains are mutants blocked in the citrate cycle, in phosphoenolpyruvate carboxykinase or one of the glycerolphosphate dehydrogenases (NAD dependent or independent). A mutant lacking phosphoglycerate kinase activity and able to grow on glucose and L-malate but not on either carbon source alone, can also be induced to sporulate in a medium containing both glucose and malate. Among other sporulation mutants whose biochemical deficiency is not known, some are weakly inducible whereas many, blocked at sporulation stages O, II, III, or IV, are not inducible. The results show that the functions of the citrate cycle (used for ATP synthesis) and of gluconeogenesis (used for glycerol phosphate and D-glucosamine-6-phosphate synthesis), normally needed for sporulation under conditions of carbohydrate deprivation, are no longer required when sporulation is induced by decoyinine in the presence of carbohydrates. Mutants in which sporulation is highly inducible can be used as a sensitive tool for the detection of other inducing compounds because their spontaneous (uninduced) background of spores is very low.