The Occurrence of Actual F Factor Transfer during the Stationary-phase Mutation in Escherichia coli FC40

The experiment of adaptive mutation was performed by using Escherichia coli GM133 rif as test cells and HB214 strr as scavenger cells. Transfer frequency between GM133 and HB214 was estimated,based on the number of revertants appeared on the selective plates when GM133 were killed by addition of M9 selective medium containing 100μg/mL of streptomycin at different time. After 30 minutes the cells of GM133 and HB214 were mixed, the estimated transfer frequency was about 0. 07% ,and two days,7. 47%. After selection of 7 days,some HB214 cells with F factor from GM133 cells and Lac+ mutation were observed,but these cells failed to form the colonies which can be seen by the naked-eye. It was demonstrated that actual P factor transfer events from test cells GM133 to scavenger cells HB214 occurred during the selection.