TABLE 1.
Enzymatic determination of benzyl viologen-dependent nitrate and nitrite reductase activities
| B. subtilis strain | Avg activity ± SD (10−3 U/mg of protein)a
|
|
|---|---|---|
| Nitrate reductase | Nitrite reductase | |
| JH642 (wild type) | 330 ± 10 | 6,100 ± 220 |
| THB1 (narG mutant) | ND | 5,600 ± 280 |
| THB2 (fnr mutant) | ND | 9,900 ± 310 |
| MH5081 (resDE mutant) | 50 ± 10 | ND |
a
Benzyl viologen-dependent dissimilatory activities determined in vitro with cell extracts prepared from the B. subtilis strains after anaerobic growth on nitrate- and nitrite-containing medium. One unit of activity corresponded to the reduction of 1 μmol of nitrite or nitrate per min. See the text for detailed assay conditions. Values reported are the averages from at least three independent experiments performed in triplicate. ND, not detectable.