title: Nitrogen fixation in methanogens: the archaeal perspective.
abstract: The methanogenic Archaea bring a broadened perspective to the field of nitrogen fixation. Biochemical and genetic studies show that nitrogen fixation in Archaea is evolutionarily related to nitrogen fixation in Bacteria and operates by the same fundamental mechanism. At least six nif genes present in Bacteria (nif H, D, K, E, N and X) are also found in the diazotrophic methanogens. Most nitrogenases in methanogens are probably of the molybdenum type. However, differences exist in gene organization and regulation. All six known nif genes of methanogens, plus two homologues of the bacterial nitrogen sensor-regulator glnB, occur in a single operon in Methanococcus maripaludis. nif gene transcription in methanogens is regulated by what appears to be a classical prokaryotic repression mechanism. At least one aspect of regulation, post-transcriptional ammonia switch-off, involves novel members of the glnB family. Phylogenetic analysis suggests that nitrogen fixation may have originated in a common ancestor of the Bacteria and the Archaea.
authors.affiliation: Dept Microbiology, University of Washington, Seattle 98195, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Leigh
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D019641:DNA, Archaeal / Q000235:genetics; D019605:Euryarchaeota / Q000235:genetics* / Q000378:metabolism*; D019143:Evolution, Molecular; D019848:Gene Expression Regulation, Archaeal; D019766:Genes, Archaeal; D005798:Genes, Bacterial; D008670:Metals / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D009586:Nitrogen Fixation / Q000235:genetics; D051922:PII Nitrogen Regulatory Proteins; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D019641:DNA, Archaeal; D008670:Metals; D051922:PII Nitrogen Regulatory Proteins; C404143:PIID regulatory protein, Bacteria