Penetration of nalidixic acid in the cell cycle of Escherichia coli K-12.

Diffusion of nalidixic acid (NAL), DNA synthesis and filamentation of Escherichia coli K-12 cells induced by the drug were investigated in the division cycle. It was found that in nonsynchronous culture and within the range of sublethal NAL concentrations the length of the filaments depends on the dose or the time of action of the drug. In synchronous culture differences are observed in the values of measured parametres between samples from the successive culture phases. Maximum [3H] NAL penetration and DNA synthesis inhibition caused by the drug were noted in the period proceeding directly division. The extent of NAL penetration into the cell in the sample is correlated with the change in length of the NAL-induced filamentous cells.