Deletion of rovM in Y. pestis confers a competitive fitness defect while the complemented mutant, rovM (pACrovM) has a competitive fitness advantage, during flea infection.

Percentage infection per flea at 0 and 28 day post-infection, with (A) a rovM mutant and wild type strain or, (B) rovM (pACrovM) and the wild type strain. The mean of the percentage infection for 16–20 fleas is indicated by the horizontal bar. A student’s t-test was used to determine the significant differences between the percentage infections of each strain in fleas. The P values are given. Black symbols represent the first infection and grey symbols the second infection.