TABLE 2.
Effect of a modE allele on napF-lacZ expression in response to anaerobiosis and addition of nitrate
| Strain | Relevant genotypea | β-Galactosidase activityb
|
|||||
|---|---|---|---|---|---|---|---|
| + O2, NA | −O2
|
||||||
| NA | +NO2− | +NO3− | +Mo | +NO3−, +Mo | |||
| MC4100(pACYC184) | λHW2 | 50 | 280 | 1,900 | 1,250 | 265 | 1,300 |
| PM8(pACYC184) | λHW2 modE | 25 | 85 | 170 | 130 | 85 | 125 |
| PM8(pPM6) | λHW2 modE (modE+) | 55 | 320 | 2,000 | 1,320 | 300 | 1,350 |
| PM6(pACYC184) | λHW2 modE modC | 25 | 90 | NDc | 130 | 90 | 135 |
| PM6(pPM6) | λHW2 modE modC (modE+) | 30 | 425 | ND | 140 | 305 | 1,350 |
| PM6(pPM9) | λHW2 modE modC (modE∗) | 55 | 2,340 | ND | 1,440 | 330 | 1,400 |
a
λHW2 is a prophage, inserted in the chromosome of the indicated strains in single copy, carrying a napF-lacZ operon fusion. Genes, present on multicopy plasmids are shown in parentheses.
b
Units are given in nanomoles of ONPG hydrolyzed per minute per milligram of protein. Cells were grown in minimal glucose medium under aerobic and anaerobic conditions as described in the text. Sodium nitrate (NO3−), sodium nitrite (NO2−), and sodium molybdate (Mo) were added where indicated at 40 mM, 2.5 mM, and 100 μM, respectively; NA, no addition of nitrate, nitrite, or molybdate.
c
ND, not determined.