TABLE 2.

Symbiotic nitrogen fixation and H2 metabolism of hupSL mutants from Bradyrhizobium sp. (Lupinus) Z89 and Bradyrhizobium sp. (Vigna) M5a

StrainGenotypeHydrogenase activitybH2 evolutioncNitrogenase activitydREe
Z89Wild type1,740 ± 2600.3 ± 0.221.3 ± 0.20.99
Z89.1Z89 hupSL::pSCB250 ± 105.3 ± 0.421.5 ± 2.80.76
M5Wild type1,710 ± 70<0.120.3 ± 2.61
M5.1M5 hupSL::pSCB340 ± 103.9 ± 0.615.8 ± 1.20.75
  • a Values were determined 30 days after inoculation.

  • b Hydrogenase activities were determined in bacteroid suspensions and are expressed in nmol H2 h−1 (mg prot)−1. Values are averages of four determinations with two replicates ± standard errors.

  • c Expressed as μmol H2 h−1 g−1 (fresh weight of nodules). Values are averages of four determinations with two replicates ± standard errors.

  • d Expressed as μmol C2H2 reduced h−1 g−1 (fresh weight of nodules). Values are averages of four determinations with four replicates ± standard error.

  • e Relative efficiency (RE) was calculated as 1 − (H2 evolution/C2H2 reduction).