Fig 3.

Proposed model of MtrF regulation, including NrrF. (A) Under Fe-replete conditions, MpeR and NrrF transcription is repressed by Fur, relieving MpeR-mediated repression of mtrF and nominal effects of NrrF on either mtrF or NGO1024 transcripts. (B) Under low-Fe conditions, transcription of MpeR and NrrF is derepressed, allowing MpeR to suppress MtrR and MtrF transcription, and allowing increased message turnover of mtrF and NGO1024 by NrrF. Solid perpendicular lines indicate repression of the transcript, and dashed perpendicular lines indicate derepression. Solid lines with filled circles represent enhanced message degradation by NrrF; conversely, diminution of the effects of NrrF are represented by dashed lines with open circles. P, promoter region.