Expression Of Nitrogen-fixing Genes In Synechocystis Sp.PCC6803 And Isolation And Identification Of Nitrogen-fixation Bacteria

This research integrated Cyanothece sp.PCC 8801nifHDK and Heliobacterium chlorum nifHDK into the genome of the unicellular non-nitrogen fixation cyanobacterium-Synechocytis,sp.PCC 6803 using pfq20,an efficient gene expression vector in Synechocystis sp.PCC6803,and detect the transcription and expression of these nif genes.Results showed that nifHDK genes from both microoganisms transcribed in Synechocystis sp.PCC 6803.However,only NifH protein from Heliobacterium chlorum was detected in western blot experiments.Further,we linked the promoters of gene PmgRl of Synechocystis sp.PCC 6803,gene nifB and nifH of Cyanothece sp.PCC 8801 to Cyanothece sp.PCC 8801nifH gene individually,and detected its transcription and expression.Results showed that NifH proteins under three promoters were expressed at different levels,and the transcription level under PmgRl promoter was effected significantly by light condition,which was enhanced under dark condition.On the other hand,we isolated two strains T3 and T22 from rhizosphere soil of Alhagi sparsifolia using Doberener medium without nitrogen,and identified them from physiological and biochemical characteristics,chemical components comparasion,genetic and phylogenetic analysis.Strain T3 represents a novel species of the genus Pseudomonas,for which the name Pseudomonas urumqiensis sp.nov.,is proposed.The type strain is T3T(=ACCC 60124T=JCM 32830T).Strain T22 represents a novel species of the genus Chitinophaga,for which the name Chitinophaga alhagiae sp.nov.,is proposed.The type strain is T22T(= ACCC 60125T=KCTC 62518T).