Table 1. Modulation of EHEC virulence program by microenvironmental cues in the human gastrointestinal tract.
| Local GIT Environment | Cue | Regulons Involved | Virulence factors: expression changes | Virulence modulation | References |
|---|---|---|---|---|---|
| Stomach |
Low pH |
RpoS, CRP, H-NS, GadE |
↑ AR1–4, ↑ Flagella and motility genes, ↑ novel adhesins ↓ LEE genes |
↑ acid resistance, ↑ motility ↑ adhesion |
66, 73 and 77 |
| Duodenum |
Bile |
BasRS, PhoP? |
↑ arnBCADTEF ↑ acrAB ↓ stx2 |
LPS modification, ↑ Bile and CAMP resistance |
69 and 89 |
| Ileum |
AI-3(quorum sensing) |
QseCB, SdiA |
↑ gad genes, flagella |
↑motility, ↑acid resistance (to SCFAs?) |
81 and 115 |
| SCFA (< 25 mM) |
↑ LEE, flagella |
↑ adhesion, ↑ motility |
112,113 |
||
| Colon |
EA |
EutR, Ler, QseE, QseC |
↑ Stx2a |
↑ cytotoxicity |
70 |
| SCFA (> 50 mM) |
↑ Iha |
↑ adhesion, ↑ iron scavenging |
114 |
||
| |
Low oxygen |
Fnr, AcrA |
↑ EspA, ↑ TTSS effectors(at microaerobic oxygen levels) |
↑ adhesion, A/E lesion |
132 and 133 |
| Epinephrine, norepinephrine |
QseCB, QseCF, QseC/KdpE |
↑ flagella ↑ LEE genes ↑ Stx |
↑ motility, ↑ A/E lesion ↑ cytotoxicity |
117 |
|
| Epinephrine, phosphate, sulfate | QseE | Inhibits RcsB,↓ LEE? | ↓ A/E lesion? | 79 |
Cues encountered at various locations within the GIT are provided along with associated changes in the expression of specific virulence factors and properties (increased, ↑, or decreased, ↓). Regulons reported to be involved in the responses are also provided.