For SPI3 , the PhoP-activated mgtCBR operon [ 40 ] was up-regulated > 15 fold within mac-rophages , while other SPI3 genes ( slsA , marT and rhuM ) were moderately up-regulated .
Interestingly , when Salmonella was grown in low Mg2 + to induce PhoP-activated transcription , multiple short transcripts were detected with a radiolabeled DNA probe corresponding to the mgtCBR leader region ( 22 ) .