Proton efflux coupled to dark H2 oxidation in whole cells of a marine sulfur photosynthetic bacterium (Chromatium sp. strain Miami PBS1071)

Electrochemical measurement of trace concentrations of biological hydrogen produced by Enterobacteriaceae

Accurate measurements of the hydrogen gas produced by Escherichia coli and Hafnia alvei pure cultures during glucose metabolism were performed under different growth conditions: stagnant, with magnetic stirring or with vibrational shaking. These measurements were carried out using an electrochemical hydrogen sensor based on a platinum-coated solid polymer electrolyte membrane (Pt-SPE). The results obtained were dependent on the hydrodynamic conditions of the growth, with greater hydrogen production being associated with the stagnant conditions. These measurements will eventually enable us to elucidate whether the pathway used for glucose metabolism is either strictly or mainly anaerobic and to modify experimental conditions so as to influence the reaction.

Comparative Amperometric Study of Uptake Hydrogenase and Hydrogen Photoproduction Activities between Heterocystous Cyanobacterium Anabaena cylindrica B629 and Nonheterocystous Cyanobacterium Oscillatoria sp. Strain Miami BG7

Heterocystous filamentous cyanobacterium Anabaena cylindrica B629 and nonheterocystous filamentous cyanobacterium Oscillatoria sp. strain Miami BG7 were cultured in media with N 2 as the sole nitrogen source; and activities of oxygen-dependent hydrogen uptake, photohydrogen production, photooxygen evolution, and respiration were compared amperometrically under the same or similar experimental conditions for both strains. Distinct differences in these activities were observed in both strains. The rates of hydrogen photoproduction and hydrogen accumulation were significantly higher in Oscillatoria sp. strain BG7 than in A. cylindrica B629 at every light intensity tested. The major reason for the difference was attributable to the fact that the heterocystous cyanobacterium had a high rate of oxygen-dependent hydrogen consumption activity and the nonheterocystous cyanobacterium did not. The activity of oxygen photoevolution and respiration also contributed to the difference. Oscillatoria sp. strain BG7 had lower O 2 evolution and higher respiration than did A. cylindrica B629. Thus, the effect of O 2 on hydrogen photoproduction was minimized in Oscillatoria sp. strain BG7.