Recent studies indicate that HilA binds to specific sequences in the prgH promoters .
It is known that prgH is under the regulation of HilA .
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 ) .