Figure 6.

Competence is beneficial during transient exposure to rifampicin. (A) Typical time lapse series of P_comKgfp (BD2711) outgrowth after rifampicin exposure. Bacteria were grown to T₂, diluted and subsequently inoculated into a microscopy flow chamber. Fresh competence medium containing 10 μg/ml rifampicin was flushed through the flow chamber for 1 h. Afterwards, fresh competence medium without antibiotics was continuously applied, and cells were imaged. DIC and fluorescence images were merged; orange, GFP fluorescence. Arrows depict cells that eventually initiate growth. Scale bars: 10 μm. (B) Fractions of competent and non-competent cells that re-initiated growth (N = 3409 cells, error bars: standard deviation from three independent experiments). (C,D) Competition experiment between (C) wt (BD630) and ΔcomK gfp (Bs140) and (D) Δrok (Bs056) and ΔcomK gfp. Competitors were grown separately to T₂, diluted into fresh competence medium containing rifampicin as detailed in the graphs, and mixed in a 1:1 ratio. At t = 1 h, antibiotics were washed out and fresh competence medium was added. Upper graphs: growth curves (optical density). Lower graphs: fraction of (C) wt and (D) Δrok cells competing against non-competent ΔcomK gfp cells. Each graph is a representative result of at least three independent experiments.