FIG 3.

Antagonism depends on a hard surface and OmrA. (A) An A⁺ S⁻ strain labeled with GFP (DW709, tra⁺) was mixed at a 1:1 ratio with a nonmotile aggressor strain (DW1048; mCherry) and placed on hard agar (HA; 1.5%) or soft agar (SA; 0.5%). As a control, a traA::km mutant (A⁺ S⁻, DW1613) was mixed with DW1048 on HA. (B) An omrA mutation confers resistance. Indicated A-motile strains (omrA, DW1617; omrB, DW1618; control, DW1619) were incubated with a nonmotile aggressor strain (DK8606; GFP labeled). Three independent experiments were carried out, and the data are plotted as the means ± standard errors. All strain ratios were determined by fluorescence microscopy.