prgI are known to be repressed , respectively , by the active form of PhoP .
Additionally , transcription of many genes in SPI-1 declined in Δpat , including the prg ( PhoP-repressed products ) genes prgK , prgJ , prgI , and prgH ( to ) , encoding component of the needle complex ; the sip ( Salmonella invasion protein ) genes sipA , sipD , sipC , and sipB ( approximately ) , encoding translocation machinery component ; and the inv ( invasion ) genes invJ , invI , invC , invB , invA , invE , invG , invF , and invH ( approximately ) , which were essential for invasion of cells ( Supplementary Table 4 ) .