Study On The Mechanism Of NaHSO₃ Regulated Photosynthetic H₂ Production In Anabaena Sp. Strain PCC 7120

At least three enzymes have been confirmed to be involved in the photosynthetic H₂ production in Anabaena sp. strain PCC 7120, nitrogenase, bi-directional hydrogenase and uptake-hydrogenase. The formal research has proved that the nitrogenase is the primary protein that produces the H₂ in Anabaena sp. strain PCC 7120. However, nitrogenase and bi-directional hydrogenase are very sensitive to O₂, which leads to the low efficiency of photosynthetic H₂ production in Anabaena sp. strain PCC 7120. The modulate concentration of NaHSO₃ can decrease the photosynthetic O₂ evolution in cyanobacteria, which indicate that the activity of nitrogenase and bi-directional hydrogenase in Anabaena sp. strain PCC 7120 may be effected by NaHSO₃ resulted O₂ decreasing in the cell. Therefore, the photosynthetic H₂ production can be regulated by the NaHSO₃ treatment.The O₂ content in the cell could be affected by treatment with different concentrations of NaHSO₃. The photosynthetic O₂ evolution rate could be inhibited significantly when the cell treated with 0.1 mM NaHSO₃, and the highest rate of H₂ production was obtained when the concentration reached 1.0 mM. Nitrogenase and bi-directional hydrogenase were involved in H₂ production in Anabaena sp. strain PCC 7120. From the morphological characterization of 1.0 mM NaHSO₃ treated cell, we suggested that the activity of NaHSO₃ on heterocyst was the main reason which caused the high rate of photosynthetic H₂ production in Anabaena sp. strain PCC 7120. And our further research of the expression and the activity of nitrogenase revealed that this enzyme was the target protein under NaHSO₃ treatment.Cyanobacteria is the simple photoautotrophic microorganism, it can photolysis the H₂O into electron and proton which can be used to produce H₂ through the electron pathway and the redox reaction in the cell. To study the possible molecular mechanism of such enhancement of photosynthetic H₂ produced efficiency in Anabaena sp. strain PCC 7120, we investigated the activity of photosynthetic electron transport which was related to the photosynthetic H₂ production in the NaHSO₃ treated cell. After the analysis and the comparison of these electron transport, we found that the activity of some photosynthetic electron pathway had significant influence on photosynthetic H₂ production in NaHSO₃ treated Anabaena sp. strain PCC 7120, and the electron that flow to the CO₂ assimilation of the cell was proved to be the most important in these influences. So, the inhibition of the electron pathway of CO₂ assimilation was regarded as the primary cause which leads the significant enhancement of photosynthetic H₂ production in Anabaena sp. strain PCC 7120.