Fig. 4

KIM6+ and CO92 are equally fit during competitive co-infection in fleas. Xenopsylla cheopis fleas were co-infected with a 1:1 ratio of CO92 and KIM6+::kan^R. The Y. pestis bacterial loads were determined for 18–20 fleas at time points 0 (2 h post-acquisition of the co-infected blood meal), 7 and 14 days post-infection. The percentage of KIM6+::kan^R in the co-infection was determined and plotted for each time point. One of two independent experiments with similar outcomes is shown. A Student’s t-test was used to determine statistical significance between time points. Abbreviation: ns, not significant