Recombinant plasmid that carries part of the nitrogen fixation (nif) gene cluster of Klebsiella pneumoniae.

Abstract
Fragments of the K. pneumoniae genome that carry part of the his operon and part of the N2 fixation (nif) gene cluster were cloned on the amplifiable plasmid pMB9. One particular plasmid, pCRA37, complements mutations in the hisD, nifB and nifF loci. The physical map of pCRA37, as determined by [EcoRI and SalI] restriction enzyme analysis, correlates with the genetic map of the his-nif region as determined previously by phage P1-mediated cotransductional analysis.