Fig. 1.

Genetic and antigenic/immunologic analyses of the Δcaf mutant of Y. pestis CO92. (A) Genomic DNA from both the WT and its Δcaf mutant was isolated, and the specific primers were used to PCR amplify the coding region of the caf1 gene. (B and C) Western blot analysis with specific antibodies to the F1 antigen (B) or the LcrV antigen (C) were used for examining the production of corresponding proteins in both the WT and its Δcaf mutant. (D) Both the WT (left) and its Δcaf mutant (right) were subjected to staining with specific anti-F1 antibody, followed by detection with Alexa-488-labeled (green) secondary antibody using a fluorescent microscope. (E) The production of F1 by the WT (green line) and the Δcaf mutant (black line) was further evaluated by flow cytometry using antibody specific to F1 or an isotype-matched control (red line), followed by detection with fluorescence-labeled (Alexa-488) secondary antibody.