Fig. 2: Experimentally measured effects of environmental conditions (evaporative, EV; Marangoni convection, MC; non-evaporative, NEV) on the extent of RP4 conjugation and the relative expression levels of conjugation-related genes.

The effects of (A) the initial cell number, (B) mating temperature, and (C) mating time. For the initial cell number and mating temperature (A and B), experimental replicates (n = 3) are depicted as filled circles and analytical replicates (n = 3 per experimental replicate) are depicted as open circles. Some datapoints are not visible due to overlap with other datapoints. Statistically significant (≤0.05) Holm–Bonferroni adjusted P values are reported for relevant factor level comparisons (among levels of initial cell number or mating temperature within each evaporation condition). For all data (A, B, C), statistically significant differences between evaporation conditions are depicted with lower-case letters. D Relative expression levels of genes encoding conjugation-related membrane proteins (ompA), involved in mating pair formation (trbBp and traF) and involved with plasmid transfer and replication (trfAp and traJ). Expression levels are relative to those measured for EV conditions. Statistically significant (≤0.05) Holm–Bonferroni adjusted P values are reported for comparisons between the gene expression levels of the MC and NEV treatments against the EV treatment. The degree of statistical significance is indicated with *, ** or *** for P values that are 0.05–0.01, 0.01–0.001 or <0.001, respectively. Differences in the spatial distributions of cells and their cell-cell interactions under (E) non-evaporative and (F) evaporative conditions. Dotted lines in (E) represent bacterial trajectories of random motion and arrow thickness represents the magnitude of effective plasmid conjugation or conjugation-related gene expression.