Fig. 1: Droplet size effect on plasmid transfer rates.
A A representative section of the glass surface covered by sprayed droplets at 6 h after spraying. Green cells are trans-conjugants. Inset: zooming into individual droplets. Donor, recipient, and trans-conjugant cells are shown in red, black, and green respectively. B Droplet area histogram (‘area’ refers to the area of the liquid <> solid interface, A). C The total number of cells (N) in individual droplets (including donors, recipients, and trans-conjugates at t = 6 h). Circle size reflects droplet area. Axis plotted in log-log scale (dataset includes 372 droplets). D Surface cell density in individual droplets. Line shows smoothed average (using LOESS), circles represent mean ± STD for binned data. ρ represents Spearman rank correlation coefficients (P < 10e-10). E Lines show cumulative number of transfer events over time in individual droplets at 3, 6, 12, and 18 h post inoculation (semi-log scale). Solid black line represents mean ± SE (SE smaller than symbols). F Number of transfer events as a function of droplet area: Circles are experimental data. Black line: mechanistic model Te = 3.58·10−7·A1.62 (SI). Dashed line: best-fitted line based on data Te = 1.08·10−9·A2.12 (fitted as a power law, SI). Inset: same data, but at log-log scale. G Transfer events per cell (Tc) as a function of droplet area. Black line is smoothed data (LOESS). ρ represents Spearman rank correlation coefficients (P < 10e-10). H Conceptual representation of the underlying mechanisms explaining the increase in plasmid transfers as a function of droplet area. In (F) and (G), droplets are shown only for A > 103.9 µm2 (smaller droplets show mostly zero transfers).
