Study On Mechanism Of Iron Deficiency Improving Photosynthetic Hydrogen Production Induced By NaHSO₃ In Microalgae

Since 21 st century,the increasing shortage of fossil fuels,greenhouse effect and environmental pollution caused by the combustion of traditional energy prompted us to look for a new,clean and renewable energy.When hydrogen is burned,it gives out high energy with just water only,which makes it being widely concerned as a renewable energy sources among the numerous biomass energy.In this situation,biological hydrogen production processed by photosynthetic algae is becoming a major research direction.However,hydrogen can only be released in extremely special anaerobic circumstance by microalgae.Due to the sensitivity of oxygen by hydrogenase,many methods like nutrients deprivation,cell aggregation,light-dark culture and genetic engineering for hydrogenase are all ongoing to create an anaerobic environment for bio-hydrogen production from microalgae.Although these methods can enhance hydrogen production of microalgae,they also have risks and flaws like limiting the electron source of hydrogen production,fussy or uneconomic.In this thesis,we selected Synechocystis sp.PCC 6803 as a model organism because it has an ordinary biological background and genetic operation.As a photosynthetic organisms with Ni-Fe bidirectional hydrogenase,Synechocystis sp.PCC 6803 can product hydrogen under anaerobic environment.Therefore we used the tagging library of Synechocystis sp.PCC 6803 to search for a mutants with a high PSII activity under anaerobic environment with NaHSO₃ addition,and we named it as?m86 mutant.The main research results are as follows:?1?We isolated two mutants from the transposon-tagging library of Synechocystis sp.PCC 6803 with higher PSII activity and hydrogen production when NaHSO₃ is added to the culture medium.We used reverse PCR to analyze the sites of transposons insertion in both mutants.Finally we found that the unknown gene m86 was inserted by transposons in both mutants.?2?Through analyzing the unknown protein M86,we found that M86 is aphotosynthesis-specific protein in microalgae.Our data indicated that M86 is involved in iron transport.These analyses of ?m86 growth,iron content,and marker gene of iron deficiency or overexpressed strain?overexpressing m86 into one deletion mutant of iron transport protein?of different species showed that the absence of m86,reduced the intracellular iron level.?3?In organisms,iron,as one of the factors of cell growth,can often generate more ROS through Fenton reaction.We proved that less iron can reduce the toxicity of NaHSO₃ on PSII activity and reducing intracellular iron can achieve a higher hydrogen production in Chlamydomonas reinhardtii.Our thesis reveals the function of an unknown genes and provides a new promotion on the microalgae hydrogen production.