Table 1.
Effects of mutations in palindromes on nifH expression
| Construct or PnifH mutation | β-gal, ammonia-grown | β-gal, N2-grown | Ratio NH4+/N2 |
|---|---|---|---|
| Wild-type M. maripaludis | 2.4 ± 1.8 | 5.7 ± 3.5 | |
| Pmcr-lacZ | 282.0 ± 19.2 | 351.5 ± 106.8 | |
| No promoter-lacZ | 1.9 ± 0.8 | 2.0 ± 0.6 | |
| PnifH-lacZ | 3.1 ± 0.7 | 140.7 ± 17.9 | 0.01 |
| CT1 | 23.7 ± 6.6 | 34.7 ± 11.9 | 0.66 |
| AG1 | 62.3 ± 2.3 | 179.9 ± 57.0 | 0.34 |
| AG1 | 75.6 ± 3.4 | 290.1 ± 63.5 | 0.26 |
| CT1AG1 | 585.4 ± 41.9 | 844.4 ± 86.3 | 0.69 |
| TA3T | 5.2 ± 1.4 | 61.4 ± 28.3 | 0.05 |
| TA3T | 2.8 ± 0.7 | 172.7 ± 41.8 | 0.01 |
| CT2 | 13.1 ± 0.5 | 194.1 ± 34.1 | 0.06 |
| AG2 | 4.4 ± 1.9 | 96.8 ± 21.5 | 0.03 |
| CT2AG2 | 9.7 ± 1.7 | 356.8 ± 27.2 | 0.02 |
| Δ6 | 9.6 ± 1.0 | 393.0 ± 50.4 | 0.02 |
Each line presents data from a separate strain of M. maripaludis. Strains were grown in nitrogen-free medium under N2 in the presence (ammonia grown) or absence (N2 grown) of NH4+. Portions of cultures (0.2 ml) were used for β-gal measurements according to Miller (24). Values are averages from triplicate samples. Ratio NH4+/N2 was calculated after subtracting background. Additional experiments showed similar trends.