Distribution and evolution of nitrogen fixation genes in the phylum Bacteroidetes

Jun Ichi Inoue, Kenshiro Oshima, Wataru Suda, Mitsuo Sakamoto, Takao Iino, Satoko Noda, Yuichi Hongoh, Masahira Hattori, Moriya Ohkuma*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)


Diazotrophs had not previously been identified among bacterial species in the phylum Bacteroidetes until the rapid expansion of bacterial genome sequences, which revealed the presence of nitrogen fixation (nif) genes in this phylum. We herein determined the draft genome sequences of Bacteroides graminisolvens JCM 15093T and Geofilum rubicundum JCM 15548 T. In addition to these and previously reported ‘Candidatus Azobacteroides pseudotrichonymphae’ and Paludibacter propionicigenes, an extensive survey of the genome sequences of diverse Bacteroidetes members revealed the presence of a set of nif genes (nifHDKENB) in strains of Dysgonomonas gadei, Dysgonomonas capnocytophagoides, Saccharicrinis fermentans, and Alkaliflexus imshenetskii. These eight species belonged to and were distributed sporadically within the order Bacteroidales. Acetylene reduction activity was detected in the five species examined, strongly suggesting their diazotrophic nature. Phylogenetic analyses showed monophyletic clustering of the six Nif protein sequences in the eight Bacteroidales species, implying that nitrogen fixation is ancestral to Bacteroidales and has been retained in these species, but lost in many other lineages. The identification of nif genes in Bacteroidales facilitates the prediction of the organismal origins of related sequences directly obtained from various environments.

Original languageEnglish
Pages (from-to)44-50
Number of pages7
JournalMicrobes and Environments
Issue number1
Publication statusPublished - 2015
Externally publishedYes


  • Bacteroidales
  • Nif gene
  • Nitrogenase
  • Symbiosis
  • Termite

ASJC Scopus subject areas

  • Plant Science
  • Soil Science
  • Ecology, Evolution, Behavior and Systematics


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