TABLE 4.
Nitrogenase activity in K. pneumoniae strains with pCK3 (K. pneumoniae nifA) and its response to NH4Cl in the presence of either 10 or 50 μM IPTG in the derepression medium
| IPTG concn (μM) and strain | Chromosomal genotypea | Gene(s) on plasmidsb | Nitrogenase activityc
|
|
|---|---|---|---|---|
| Initial | 40 min after NH4Cl was added (%)d | |||
| 50 | ||||
| UN5513 | wt | nifA | 950 | 980 (104) |
| UN5514 | glnB | nifA | 870 | 980 (113) |
| UN5515 | glnK | nifA | 800 | 1,200 (150) |
| UN5516 | wt | draTGB, nifA | 1,000 | 8 (1) |
| UN5517 | glnB | draTGB, nifA | 700 | 320 (46) |
| UN5518 | glnK | draTGB, nifA | 990 | 1,180 (119) |
| UN5519 | wt | draT, nifA | 580 | 6 (1) |
| UN5520 | glnB | draT, nifA | 80 | 6 (8) |
| UN5521 | glnK | draT, nifA | 630 | 7 (1) |
| 10 | ||||
| UN5516 | wt | draTGB, nifA | 810 | 80 (10) |
| UN5517 | glnB | draTGB, nifA | 780 | 500 (64) |
| UN5518 | glnK | draTGB, nifA | 930 | 1,400 (150) |
| UN5519 | wt | draT, nifA | 850 | 9 (1) |
| UN5520 | glnB | draT, nifA | 480 | 5 (1) |
| UN5521 | glnK | draT, nifA | 1,010 | 7 (1) |
a
wt, wild type.
b
nifA was from K. pneumoniae; draT, draG, and draB were from R. rubrum.
c
Each unit of nitrogenase activity is expressed as nanomoles of ethylene produced per hour per milliliter of cells at an optical density at 600 nm of 1. Each activity value is from at least three replicate assays from different individually grown cultures. The deviation is <15%.
d
NH4Cl was added at a final concentration of 10 mM. The percentage of initial nitrogenase activity that remained after the NH4Cl treatments is indicated in parentheses.