TABLE 1.

β-Galactosidase activities of norR- and norV-lacZ fusions in anaerobic cultures of a wild-type strain (DH10B) and its norR and norVW mutant derivativesa

StrainPromoterβ-Galactosidase activity (Miller units)
LGLG + SNPM9M9 + SNPM9 + nitriteM9 + nitrate
DH10BnorV3 ± 146 ± 26 ± 122 ± 16 ± 135 ± 4
norR::camnorV4 ± 14 ± 114 ± 19 ± 114 ± 114 ± 1
norVW::camnorV16 ± 1b10 ± 212 ± 24 ± 194 ± 12
DH10BnorR46 ± 246 ± 2119 ± 245 ± 286 ± 10166 ± 11
norR::camnorR215 ± 12250 ± 62805 ± 33344 ± 7431 ± 561,063 ± 11
norVW::camnorR27 ± 1b14 ± 22 ± 111 ± 213 ± 1
  • a Activities were determined in duplicate from three independently grown cultures; standard errors are shown. Growth was to log phase in L broth supplemented with glucose (LG) and with 100 μM sodium nitroprusside (SNP) where indicated, or in M9 minimal medium supplemented with SNP (100 μM), nitrite (2 mM), or nitrate (50 mM), as indicated.

  • b Assays were on cultures grown in the presence of 25 μM SNP, since the higher concentration was growth inhibitory to this strain under these conditions.