88] Tests on nif probes and DNA hybridizations

Abstract

Publisher Summary This chapter discusses tests on nif probes and DNA hybridizations. The molecular genetics of the organization and regulation of nif (nitrogen fixation) genes in cyanobacteria has been initiated in a filamentous heterocystous cyanobacterium, Anabaena sp. PCC 7120. Using DNA hybridization techniques with Klebsiella pneumoniae nif probes and DNA from vegetative cells, four genes involved in nitrogen fixation in Anabaena PCC 7120 have been identified: nifH , nifD , and nifK , encoding the polypeptide components of the nitrogenase complex, and nifS, a gene involved in Klebsiella pneumoniae in the maturation of nitrogenase. Whereas in the enterobacteria the nif structural genes are adjacent and cotranscribed, nifK is separated from nif DH by 11 kilobases of DNA in Anabaena vegetative cells. DNA hybridization methods using nif probes are not only useful in cyanobacteria to isolate nif genes and to study the nif gene organization and structure, but can also provide information for the regulation of nif gene transcription in vivo .