SPI1 and Salmonella Infections: Saini et al. (2010) proposed that the three systems involved in Salmonella infection are subject to dynamic regulation. First, Salmonella use flagella to swim to site of invasion, then SPI-1 T3SS is expressed and finally T1F are expressed. The authors suggested that the most significant regulator of these processes is the flagellar regulator FliZ, as it regulates both SPI-1 and T1F expression; however, no direct effect of FliZ on fim cluster expression was observed.