Identification and cloning of Thiobacillus ferrooxidans structural nif genes in Escherichia coli

The presence of nucleotide sequences which are homologous to the nifHDK genes of Klebsiella pneumoniae was demonstrated in total DNA preparations from five different iron-oxidizing Thiobacillus ferrooxidans strains. A non-iron-oxidizing Thiobacillus novellus strain and a heterotrophic Acidiphilium strain, which occurs in close association with T. ferrooxidans, did not contain DNA homologous to the nifHDK genes. The T. ferrooxidans ATCC33020 nifHDK genes were cloned and their arrangement was characterized on a 6.7-kb insert in pIMP16.