An allele of gyrA prevents Salmonella enterica serovar typhimurium from using succinate as a carbon source

A mutant gyrA allele resulting in an A271E substitution in the DNA gyrase protein generated astrain unable to grow on the [C.sub.4]-dicarboxylates succinate, malate, and fumarate. Bacteria harboring gyrA751 displayed decreased negative supercoiling in cells. Expression of the dctA gene, which encodes the [C.sub.4]-dicarboxylate transporter, was reduced in a gyrA751 mutant, providing the first evidence that dctA expression is supercoiling sensitive and uncovering a simple metabolic screen for lesions in gyrase that reduce negative supercoiling.