Fig 1.

Y. pestis phoP mutants are defective for flea blockage but are able to stably infect the flea digestive tract. (A) Percentages of fleas that developed proventricular blockage during the 4-week period after feeding on blood containing the Y. pestis strain indicated. (B) Percentages of fleas still infected 4 weeks after the infectious blood meal. (C) Average bacterial load per infected flea 4 weeks after the infectious blood meal. In panels A and B, the means and standard errors of the means (SEM) from two (GB ΔphoP) or three (KIM6+ strains) independent experiments are shown; the wild-type GB infection was performed only once. In panel C, the means and ranges from three independent experiments are given. *, P < 0.001 compared to wild-type parent strain by Fisher's exact test. Bars: 1, KIM6+; 2, KIM6+ ΔphoP; 3, KIM6+ ΔphoP (pLGphoP); 4, KIM6+ ΔpmrA; 5, KIM6+ ΔphoP ΔpmrA; 6, KIM6+ ΔpbgP Δugd; 7, wild-type GB; 8, GB ΔphoP.