HilA is a master regulator of SPI1 genes like sipB , sipC , sopD , sopB etc. .
Expression of the SPI-1 master regulatory gene hilA and five HilA-regulated SPI-1 genes ( sipB , spaO , invH , prgH and invF ) was tested in the loiA mutant , in comparison with the wild-type strain , grown under SPI-1-inducing conditions ( low O2 , high salt ) .