FIG. 3.

Nitroreductase (NPR) activities in crude extracts from wild-type and mutant strains of R. capsulatus B10 grown diazotrophically (A) or with 5 mM ammonium chloride (B) in the presence of 150 μM 2,4-dinitrophenol. Samples were collected at the indicated times, and crude extracts were obtained as described in Materials and Methods. •, wild-type strain; ▵, nprA mutant strain; □, nprB mutant strain; ○, nprA nprB mutant strain. Data correspond to a representative experiment which was repeated three times with variations of <12%.