(A) Percentages of fleas that developed proventricular blockage during the 4-wk period after feeding on blood containing the Y. pestis or Y. pseudotuberculosis strain indicated. (B, C) Percentages of fleas still infected (B) and average bacterial load per infected flea (C) 4 wks after the infectious blood meal. The PDE2-pstbE509A allele has a single nucleotide site-specific mutation in the EAL catalytic domain that eliminates enzyme activity, other allele notations are as in Figure 1 and Table S1. The mean and SEM (A, B) or range (C) of three independent experiments are shown; data for the Y. pestis rcsA-pstb strain are from (Sun et al., 2008). *, P < 0.0001 by Fisher's exact test; **, P = 0.007 and ***, P = 0.003 by Kruskal-Wallis test with Dunn's multiple comparison post-test.