TABLE 4.
Summary of the expression and role of the four hydrogenases in Salmonella Typhimuriuma
| Hydrogenase | Feature(s) | Reference(s) |
|---|---|---|
| Hya (Hyd-1) | Expressed during fermentative survival and regulated by FNR, ArcA | 80, 240 |
| Recycles exogenous and endogenous H2 under fermentative conditions | 81, 84 | |
| Important for acid resistance and macrophage colonization | 81 | |
| Expressed at low levels in liver, spleen, and ileum in mice | 81 | |
| Hyb (Hyd-2) | Expressed during anaerobic growth and regulated by FNR, ArcA, CRP | 80, 89, 240 |
| Supports growth by hydrogenotrophic fumarate respiration | 83, 238 | |
| Expressed in phagocytes and likely gastrointestinal tract | 81 | |
| Uses microbiota-derived H2 to invade gastrointestinal tract in mice | 13, 248, 456 | |
| Hyd (Hyd-5) | Expressed under aerobic growth and repressed by ArcA | 8, 81 |
| Mediates hydrogenotrophic aerobic respiration and is oxygen tolerant | 8, 82, 243 | |
| Strongly expressed in macrophages | 81 | |
| Expressed early in liver and spleen, later in ileum of mice | 81 | |
| Hyc (Hyd-3) | Expressed during fermentative survival and regulated by FNR, FhlA | 238, 240 |
| Forms formate hydrogen lyase complex that produces H2 | 237, 238 | |
| Important for anaerobic acid resistance | 84 | |
| Not required for colonization in murine model | 84 |
a
Findings are based on studies in pure culture and mouse models.