TABLE 5.
Effect of ammonium on the nitrogenase activity of A. brasilense strains carrying H. seropedicae NifA proteinsa
| Strain (mutation) | Plasmid (activator) | Nitrogenase activity (nmol of C2H4 · min−1 · mg of protein−1)
|
|
|---|---|---|---|
| −N | +N | ||
| FP2 (wt) | None | 19.5 | 0 |
| FP2 (wt) | pEMS135 (NifA) | 20 | 0 |
| FP2 (wt) | pEMS136 (ΔR NifA) | 18.7 | 8.6 |
| FP9 (ntrC) | None | 0 | 0 |
| FP9 (ntrC) | pEMS135 (NifA) | 0 | 0 |
| FP9 (ntrC) | pEMS136 (ΔR NifA) | 40.7 | 25.7 |
| FP10 (nifA) | None | 0 | 0 |
| FP10 (nifA) | pEMS135 (NifA) | 7.1 | 0 |
| FP10 (nifA) | pEMS136 (ΔR NifA) | 21.2 | 10.1 |
a
A. brasilense strains were grown in NFbHP medium plus NH4Cl (20 mM) and inoculated (20 μl) into semisolid NFbHP medium with or without NH4Cl (10 mM). Nitrogenase activity was measured after 18 to 24 h of incubation at 30°C as described in Materials and Methods. wt, wild type.