Mutation in the rel gene of Sorangium cellulosum affects morphological and physiological differentiation.

Interruption of the (p)ppGpp synthetase gene (rel) of Sorangium cellulosum So ce56 resulted in loss of ppGpp accumulation after norvaline treatment during exponential growth phase. The rel mutant failed to produce wild-type levels of the polyketides chivosazol and etnangien in production media. In wild-type cells expression of the chivosazol biosynthetic operon can be significantly increased by norvaline or alpha-methylglucoside. This induction does not occur in the rel mutant. The rel mutant also lost the capability to form multicellular fruiting bodies under nutrient starvation.