TABLE 3.
Effect of IPTG level on the nitrogenase activity in K. pneumoniae strains and its response to NH4Cl treatments
| Strain and genotype/ gene on plasmidsa | IPTG level (μM) | Nitrogenase activityb
|
|
|---|---|---|---|
| Initial | 30 min after NH4Cl was added (%)c | ||
| UN5510 | |||
| wt/draT | 0 | 980 | 1,170 (120) |
| wt/draT | 10 | 990 | 240 (24) |
| wt/draT | 20 | 940 | 40 (4) |
| wt/draT | 30 | 980 | 20 (2) |
| wt/draT | 50 | 780 | 15 (2) |
| UN5511 | |||
| glnB/draT | 0 | 820 | 800 (98) |
| glnB/draT | 10 | 600 | 75 (12) |
| glnB/draT | 20 | 540 | 20 (4) |
| glnB/draT | 30 | 400 | 15 (4) |
| glnB/draT | 50 | 60 | 6 (10) |
a
draT is from R. rubrum. wt, wild type.
b
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%.
c
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.