Effect of nalidixic acid on DNA replication by toluene-treated Escherichia coli.

Nalidixic acid inhibits DNA synthesis in toluene-treated E. coli, strain B/r, as it is well known to do in vivo. Both semiconservative and repair syntheses are affected, though to different degrees. Density-transfer experiments indicate that chromosomal replication is reinitiated when nalidixic acid is removed from toluene-treated cells after exposure to the acid for one generation in vivo. For cells in vivo or after toluene-treatment, reinitiation is not seen in asynchronous cultures exposed briefly to nalidixic acid or in cells prevented from synthesizing proteins during their exposure to the acid. Reinitiation occurs at the chromosomal origin but, unlike the effect seen in vivo, replication at the old site persists.