FIG. 4.

Characterization of the putative y2313-y2315-y2316-orfX operon. (A) ORF map of region from nucleotides (nt) 2545915 to 2551580 of the Y. pestis KIM chromosome (GenBank accession number AE009952.1). ORFs are shown as arrows. The coordinates of each gene are as follows: y2313, nucleotides 2547779 to 2548684; y2315, nucleotides 2548690 to 2549622; y2316, nucleotides 2549609 to 2550559; and orfX, nucleotides 2550605 to 2550559. The predicted 117-bp y2314 ORF (nucleotides 2548874 to 2548990) is on the opposite strand. The deletion strains used in this study are shown below the map, with black dotted lines indicating the endpoints of the deletions. (B) CFU assay. BMMs prepared from female C57BL/6 mice were infected with KIM6+ (white bar) or KIM6+ Δy2313-y2316 (black bar) at an MOI of 5 for 20 min and incubated in the presence of gentamicin as described in Materials and Methods. The infected cells were lysed at the indicated times, and serial dilutions of the lysates were plated to determine the number of intracellular bacteria by the CFU assay. The data represent the averages of three independent experiments. The asterisks indicate a significant difference compared to the result for KIM6+ (P < 0.01), as determined by Student's t test. The error bars indicate the standard errors of the mean (SEMs).