Construction of recombinant Escherichia coliproducing nitrogenase-related proteins from Azotobacter vinelandii

Biological nitrogen fixation by nitrogenase has attracted attention as an alternative method to chemical nitrogen fixation, which requires large amounts of fossil fuels. Azotobacter vinelandii, which produces an oxygen-sensitive nitrogenase, can fix nitrogen even under aerobic conditions; therefore, the heterologous expression of nif-related genes from A. vinelandiiis a promising strategy for developing a biological nitrogen fixation method. We assembled 17 nif-related genes, which are scattered throughout the genome of A. vinelandii, into synthetic gene clusters by overlap-extension-PCR and seamless cloning and expressed them in Escherichia coli. The transcription and translation of the 17 nif-related genes were evaluated by RT-qPCR and LC-MS/MS, respectively. The constructed E. colishowed nitrogenase activity under anaerobic and microaerobic conditions. This strain would be a useful model for examining the effect of other genes from A. vinelandiion nitrogen fixation by expressing them in addition to the minimal set of nif-related genes.Graphical AbstractAssembly of 17 nif-related genes into plasmids and expression in E. coli.