Effect of DNA gyrase inhibitors on gene expression of the cysteine regulon.

Nalidixic acid inhibits the expression of those cysteine genes which are regulated by the cysB product, it has no affect, however, on the constitutively-expressed cysE gene. The expression of cysteine genes in a strain carrying a mutation in the nalA locus is resistant to this drug. Novobiocin affects the expression of cysteine genes similarly to nalidixic acid. The effect of nalidixic acid on the expression of genes in a cysteine constitutive mutant was studied.