Organization of nitrogen-fixation genes in marine unicellular nitrogen-fixing cyanobacterium Cyanothece sp. TU126

Abstract

Some kinds of cyanobacteria have nitrogenase and fix nitrogen. Using the combination of PCR and shot-gun-sequencing methods, we identified the nif and nif-associated genes (nifJ, nifT, nifZ, nifV, nifP, nifB, fdxN, nifS, nifU, nifH, nifD, nifK, nifE, nifN, nifX, nifW, hesA, hesB and fdx) of the unicellular nitrogen-fixing cyanobacterium Cyanothece sp. TU126. Except for nifJ, the nif and nif-associated genes were arranged in the 20-kb region of Cyanothece sp. TU126 genome. We did not obtain the nifY, nifM, nifF and nifQ that were identified as nif genes in Klebsiella pnecumonnie. When the nifHDK operon encoding nitrogenase subunits was driven by T7 promoter in Escherichia coli cells, the corresponding polypeptides were detected, suggesting that the nifHDK operon also expressed as a polycistronic manner in E. coli.
This work was partly supported by METI/NEDO.