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

In this study, we aimed to monitor the extent of transitory derepression during agar surface matings in situ by comparing plasmid spread of the IncF plasmid R1 and its derepressed mutant R1drd19 at low initial cell densities. A zygotic induction strategy was used to visualize the spatial distribution of fluorescent transconjugants within the heterogeneous environment. Epifluorescence and confocal microscopy revealed different transfer patterns for both plasmids, however, spread beyond the first five recipient cell layers adjacent to the donor cells was not observed. Similar results were observed for other prototypical conjugative plasmids. These results cannot rule out that transitory derepression contributes to the limited R1 plasmid invasion, but other factors like nutrient availability or spatial structure seem to limit plasmid spread. Highlights ► 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.
Source: Plasmid - Category: Biotechnology Source Type: research