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. Author manuscript; available in PMC: 2017 Mar 26.
Published in final edited form as: Nat Microbiol. 2016 Sep 26;1:16175. doi: 10.1038/nmicrobiol.2016.175

Figure 1. Colicin producers inhibit sensitive competitors in their vicinity, promoting their own growth as well as that of nearby resistant, non-producing cheaters.

Figure 1

a, The colicin E2 operon contains toxin, immunity, and lysis genes under an SOS promoter induced by DNA damage. b, Producer strain releases colicin (red hexagons) which kills a sensitive strain, but is ineffective against a resistant strain. Strains are differentially labeled with fluoresceist reporters. c, Two-strain co-culture on solid media (containing 16 ng/mL mitomycin C) shows representative producer colonies (red) inhibiting growth of nearby sensitive (blue), but not resistant (green), colonies (scale bars = 1 mm). Sensitive colonies do not grow within the inhibition radius ri. d, Co-culture of all three strains together, showing the resistant strain can act as a production cheater. Left, growth across entire surface of representative plate; right, zoomed image of 1 cm2 box region (scale bar = 1 mm). Resistant colonies are small when competing with the sensitive strain (dash arrow) but they gain in size when growing in the vicinity of producer colonies (solid arrow).