Biophysical Monitoring And Physiological Analysis Of Synechocystis Mutants In Photosynthetic Complex

Cyanobacteria,also known as blue green algae,is a unique photosynthetic organism with strong survivability,widespread distributions and relatively simple genetic manipulation.Phycocyanobilin ferredoxin reductase gene pcy A is the key enzyme for the synthesis of phycocyanobilin(PCB),and phycoerythrobilin ferredoxin reductase gene peb S is the key enzyme for the synthesis of phycoerythrobilin(PEB).Phycocyanin(PC)and allophycocyanin(APC)are the main structural components of photosynthetic energy transfer in cyanobacteria,which play an important role in the process of light energy capture.The absorption spectrum of phycobilisomes(PBS)is mainly in the range of575-675 nm,and cyanobacteria phycobilisomes do not contain PEB whose absorption wavelength is around 560 nm.In order to fill the gap of green absorption and broaden the absorption spectrum of cyanobacteria,we want to improve the conversion efficiency of cyanobacteria to solar energy and optimize the application of cyanobacteria,this paper took a research on Synechocystis sp.PCC6803,and remoulded the structure of cyanobacteria to obtain some functional value.First,we get a mutant ?PC with "rod" deletion,a mutant with "core" deletion and a mutant ?PC/APC with "core " and " rod" deletion.With that,a PEB with green absorption was generated via transformation of peb S into the mutant and expression of peb S in vivo,then we got these mutant strains and named ?PC(Peb S),?APC(Peb S)and ?PC/APC(Peb S).Compared with WT,the growth rate measurement,spectral analysis and physiological characteristics of PEB-expressing strains showed that PEB could increase the photoheterotrophic growth rate of mutant algae.The measurement of physiological characteristics included the residual glucose in culture medium and the analysis of chlorophyll a content in algal cells.The results showed that the introduction of PEB with a blue-green spectral absorption range could promote the growth rate and chlorophyll a synthesis rate of the mutants ?PC,?APC and?PC/APC,capture light energy or other functions in photosynthesis,compensate for the lack of phycobilisomes on the energy transfer chain,and reduce the dependence on glucose.All of this are an advantage in large-scale culture.Mutant ?PC and ?PC(Peb S),?APC and ?APC(Peb S)could all induce NPQ,but mutant ?PC/APC and mutant?PC/APC(Peb S)could not induce NPQ.Mutants ?PC and ?PC(Peb S)have state transitions as well as WT,while others don't have.In addition,PCB and phycobilisomes subunits were recombined in vitro,and the results showed that OCP could quench the phycobiliprotein subunits ApcA and CpcA.