Cloning of nitrogenase structural genes from the obligate methanotroph Methylococcus capsulatus (Bath)

Southern hybridization techniques were used to examine the DNA homologies between the three nitrogenase structural genes nif</it>H, nif</it>D and nif</it>K of Klebsiella pneumoniae</it> and DNA from the obligate methane oxidizing bacterium Methylococcus capsulatus</it> (Bath). The high degree of homology between methanotroph DNA sequences and the Klebsiella</it>nif</it>H and nif</it>D genes was used to isolate and clone the corresponding Methylococcus</it>nif</it>H and nif</it>D genes. Subsequent restriction analysis revealed that all three nif</it> structural genes were contiguous in the Methylococcu</it> genome in the order nif</it>H, nif</it>D and nif</it>K, as found for the majority of other diazotrophs.