FIG 6 .

BSAP producers outcompete BSAP-sensitive strains in the mammalian gut. Isogenic strains that differed only in BSAP-1 production, sensitivity, or resistance were constructed by adding in to Bu8492 empty vector (pVector) or plasmids expressing BF638R_1646 (pBSAP-1), HMPREF1080_01556 (p01556), or BF638R_1645 (p1645). (A) Agar overlay assays of isogenic Bu8492 strains demonstrating BSAP production, sensitivity, and resistance in vitro. (B and C) Gnotobiotic mouse competitive-colonization assays between isogenic BSAP-1 producer and sensitive Omp (2 experiments, 3 mice each) (B) and BSAP-1 producer and resistant Omp (3 experiments, 3 mice each) (C). Means and standard errors are graphed. The ratios of strains in the inoculum versus day 7 feces samples were significantly different for BSAP-1 versus sensitive Omp (P = 1 × 10⁻¹⁰) but not for BSAP-1 versus resistant Omp (P > 0.05).