However, a population of pYV-free cells might well be beneficial for Yersinia during infection, similar to Salmonella enterica and Pseudomonas aeruginosa, which have T3SS-positive and T3SS-negative subpopulations (although based on a different mechanism in Salmonella SPI-1) (Rietsch and Mekalanos, 2006; Sturm et al., 2011; Rundell et al., 2016). Here, SPI1 is linked to infection.