FIG 3.

ComS overexpresser does not induce expression of comX of strain ΔcomS in coculture. (A and B) Histograms of (A) GFP and (B) RFP fluorescence of individual cells in cocultures of sender (184comS PcomX-rfp) and receiver (PcomX-gfp ΔcomS) strains in FMC medium. Strains were grown to equal levels of optical density, mixed in various proportions, and then incubated in microfluidic chambers containing stationary defined medium. Blue lines indicate population medians. Panels A and B show fluorescence of the UA159 background strain containing PcomX rfp reporter, without added XIP (negative control) (first column); of strain PcomX-gfp ΔcomS (receiver) with added 50 nM XIP (positive control) (second column); and of cocultures of sender and receiver, with columns labeled by percentage by volume of 184comS (sender) culture in the initial preparation of the coculture. (C to H) Phase-contrast images of cocultures, overlaid with red and green fluorescence images. (C) PcomX-rfp reporter in UA159 background, with no added XIP (negative control). (D) PcomX-gfp ΔcomS cells with 50 nM added XIP (positive control). (E) PcomX-gfp ΔcomS (receiver) alone, with 0% sender. (F to H) Cocultures containing 30%, 80%, and 100% sender, respectively.