A Mutant of Escherichia coli Permitting Replication of Two F Factors
Abstract
Control mechanisms of replication of bacterial genetic elements are poorly understood at present. We have studied one such mechanism involving replication of the F factor in Escherichia coli. The F factor can replicate either autonomously in F+ or F‧ strains, or as an integral part of the chromosome in Hfr strains. We have shown that presence of either an integrated F factor or a free F factor prevents replication of a second free F factor. Two integrated F factors can replicate in the same cell. The present experiments show that when a F‧lac element was transferred by mating into an Hfr strain, it had to become integrated into the chromosome in order to persist. With a recombination-deficient (recA) Hfr strain as recipient, the frequency of F‧lac integration was greatly reduced. This permitted us to isolate a mutant Hfr strain in which the F‧lac element was able to replicate autonomously. The mutation has most likely occurred in the integrated F factor itself. Availability of this new recA mutant Hfr strain facilitates genetic analysis of the F factor, since in recA+ Hfr strains frequent integration of a free F factor into the chromosome obscures recognition of complementation and recombination between two free F factors.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- March 1969
- DOI:
- 10.1073/pnas.62.3.873
- Bibcode:
- 1969PNAS...62..873M