FIG. 5.
Rate of extracellular H2 concentration change in solution following exposure to dark, anoxic conditions at 35°C. The rate of change of dissolved H2 concentration was measured using a membrane-covered electrode that irreversibly oxidizes all H2. (A) WT cells display two distinct phases of H2 production. (B) nifJ cells display a decreased phase 1 value, with the integrated area (2 ± 0.3)-fold lower. The integrated area represented by phase 2 is 18% ± 6% lower in nifJ cells. Data represent the results of one of three replicate experiments that exhibited comparable changes. (C) Model for H2 production in Synechococcus sp. strain PCC 7002. The redox poise at the diaphorase site may be increased by the presence of ferredoxin, which exchanges with NADH via transhydrogenase and FNR.