| In this study,Synechocystis sp.PCC 6803 and Anabaena sp.PCC 7120 inhabiting fresh water were selected as the host strain,with multiple promoters which are possibly induced by phosphate as the response element and luxABCDE from Photorhabdus luminescens as the reporter gene,for the construction of biosensors monitoring phosphate. And primary tests have been done on the efficiency of these biosensors.The promoter of the phoA gene encoding alkaline phosphatase and urtA encoding urea transport protein in Synechocystis sp.PCC6803 were used as the response element for the construction of the homologous recombinant plasmid pSSΩphoL and pSSΩurtL. These plasmids were transformed into wild type Synechocystis sp.PCC6803,with pSSΩlux as a control plasmid.After antibiotics selection and PCR verification,the homologous recombinant strain MsphoL and MsurtL were obtained,for the monitoring of the concentrations of phosphate in a certain fresh water environment,with MSL as the control strain.There is no difference in the growth of MsphoL and MSL in BG11 medium or in BG11 medium lacking phosphate.For MSphoL,the bioluminescence increased to about 10 times the background level 180 hours after phosphate depletion,while little change occurred in the control strain.This suggests that the MsphoL biosensor strain constructed in this study can respond specifically to the change of the phosphate concentration in the environment.In this study,some homologous genes related to phosphorus metabolism were found through bioinformatic analysis in Anbaena sp.PCC7120.The promoters of phoA(alr5291),phoD1(alr4976),pstS1(all4575),phnC(all223) and all2843 were selected as the response element for the construction of the homologous recombinant plasmid pRAΩpoAL,pRAΩpoDL,pRAΩpstL,pRAΩphnL and pRAΩa43L respectively,with pRAΩlux as the control plasmid.The construction of pRAΩpoDL and pRAΩa43L was already completed for further transformation and selection of the mutants in Anbaena sp. PCC7120. |
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