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 nifH, nifD and nifK of Klebsiella pneumoniae and DNA from the obligate methane oxidizing bacterium Methylococcus capsulatus (Bath). The high degree of homology between methanotroph DNA sequences and the Klebsiella nifH and nifD genes was used to isolate and clone the corresponding Methylococcus nifH and nifD genes. Subsequent restriction analysis revealed that all three nif structural genes were contiguous in the Methylococcus genome in the order nifH, nifD and nifK, as found for the majority of other diazotrophs.