Table 1.

Enzymatic determination of benzyl viologen-dependent nitrate and nitrite reductase activities

B. subtilisstrainAvg activity ± SD (10−3 U/mg of protein)a
Nitrate reductaseNitrite reductase
JH642 (wild type)330 ± 106,100 ± 220
THB1 (narGmutant)ND5,600 ± 280
THB2 (fnr mutant)ND9,900 ± 310
MH5081 (resDEmutant)50 ± 10ND
  • a Benzyl viologen-dependent dissimilatory activities determined in vitro with cell extracts prepared from theB. 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.