COSEGREGATION OF A SEX FACTOR WITH ESCHERICHIA COLI CHROMOSOME DURING CURING BY ACRIDINE ORANGE

We have studied the mechanism by which acridine orange cures the sex factor F′galλCI857 from cells of Escherichia coli. Under the conditions used, the loss of the episome followed first-order kinetics at a rate indicating that the acridine produced an immediate and complete cessation of episome replication. We prelabeled the bacterial DNA and followed the segregation during curing of the labeled chromosomes and the non-dividing episomes by thermoinduction and selective lysis of those cells that had inherited the prophage-bearing sex factor. During the course of curing, while the proportion of F′ cells decreased from 99 to 7% of the population, there was cosegregation of the episomes with the prelabeled strands of bacterial DNA with which they had been associated at the onset of the experiment. The result demonstrates that the inhibition of episome replication produced by acridine orange is not due to dissociation of the episome from the cellular element that is believed to constitute the bacterial unit of segregation. © 1969.