Differential effects of DNA gyrase inhibitors on the genetic transformation of Neisseria gonorrhoeae.

Inhibitors of DNA gyrase in Escherichia coli exerted differential effects on the genetic transformation of Neisseria gonorrhoeae. When competent cells of the gonococcus were exposed to novobiocin before the uptake of transforming antibiotic resistance DNA, there was a 50 to 60% reduction in the number of transformants compared with the number of control untreated cells. Norfloxacin, a more potent inhibitor of DNA gyrase and an analog of nalidixic acid, nearly abolished the production of transformants by recipient cells. On the contrary, exposure of competent cells to nalidixic acid had no effect on transformant yield. The target of these inhibitors appears to be at the level of recombination. Possible mechanisms are discussed.