Dominance of the Wild-type Alleles of Methionine Regulatory Genes in Salmonella typhimurium

Abstract

SUMMARY: Vegetative hyphae of Aspergillus niger rapidly converted caproic acid to 2-pentanone whereas germinating spores carried out the transformation slowly and ungerminated spores not at all. Glucose stimulated ketone production by germinating spores, but suppressed it in hyphae; the degree of stimulation and suppression varied with glucose concentration. This explains earlier reports that spores but not vegetative hyphae convert fatty acids to methyl ketones, since hyphae were earlier tested with high sugar concentrations, conditions where ketone formation was inhibited. Glucose disappeared from cultures containing caproate even though ketone production was inhibited, and glucose disappearance was paralleled by gluconic acid accumulation in the medium. These findings suggest that free fatty acids may play an important role in the regulation of metabolic pathways in A. niger.