In situ monitoring of IncF plasmid transfer on semi-solid agar surfaces reveals a limited invasion of plasmids in recipient colonies

► We monitored extent of IncF plasmid R1 spread during agar surface matings in situ. ► A zygotic induction strategy was used to visualize fluorescent transconjugants. ► Plasmids did not spread beyond the first five recipient cell layers adjacent to the donor cells. ► Derepressed IncF plasmid R1drd19 reduces swarming ability.