Mutants in pmrE or pmrF , two PmrA-activated loci , lack Ara4N modification to lipid-A and demonstrate reduced virulence when administered orally to mice ( 19 ) .
A drop of extracellular ion concentration from the millimolar to micromolar range can also promote PmrA-mediated upregulation of the pmrF operon .
Additionally , previously identified PmrA-activated genes , such as pmrE and pmrF that affect Ara4N biosynthesis , have been shown to play a role in virulence of S. enterica serovar Typhimurium in mice [ 7,14 ] .
Among the genes were several previously characterized PmrA-activated genes : pmrH ( STM2297 ) , pmrF , pmrC ( yjdB ) , pmrA ( basR ) , pmrB ( basS ) , yibD and pmrG ( ais ) .
The PmrA-activated pbgPE operon [ also referred to as arn ( Breazeale et al. , 2003 ) and pmrF ( Gunn et al. , 1998 ) ] consists of seven genes .