Candidate genes for this activity include mig-14 , virK and somA because inactivation of these PhoP-activated genes results in strains displaying increased susceptibility to polymyxin B ( Brodsky et al. , 2002 ; Detweiler et al. , 2003 ) .
In light of the role for SPI-2 in adaptation to the macrophage , it was interesting to observe that the macrophage-induced genes mig-3 and mig-14 , and a number of PhoP-PhoQ-activated genes also showed a dependency on Fis ( Table 3 ) .
RT-PCR analysis independently showed an NO-dependent downregulation in the transcription of PhoP-activated genes phoP , phoQ , mig-14 and phoN , while RNS treatment did not affect ( e.g. , rpoD ) or even increased ( e.g. , hmpA ) the expression of other loci ( fig. 5B ) .