Divergence in nitrogenases of Azoarcus spp., Proteobacteria of the beta subclass
- 1 July 1997
- journal article
- research article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 179 (13) , 4172-4178
- https://doi.org/10.1128/jb.179.13.4172-4178.1997
Abstract
Nitrogenase is a functionally constant protein catalyzing N2 reduction, which is found in many phylogenetic lineages of Archaea and Bacteria. A phylogenetic analysis of nif genes may provide insights into the evolution of the bacterial genomes. Moreover, it may be used to study diazotrophic communities, when classical isolation techniques may fail to detect all contributing populations. Among six species of the genus Azoarcus, diazotrophic Proteobacteria of the beta subclass, the deduced amino acid sequences of nifH genes of two species were unusually divergent from each other. Nitrogenases of the "authentic" Azoarcus branch formed a monophyletic unit with those of gamma Proteobacteria, thus being in accordance with 16S ribosomal DNA phylogeny. The nitrogenase proteins of the two aberrant strains clustered within the alpha proteobacterial clade with rhizobial nitrogenases. This relationship was supported by bootstrap values of 87 to 98% obtained by various distance and maximum parsimony methods. Phylogenetic distances of NifH proteins indicate a possible lateral gene transfer of nif genes to Azoarcus from a common donor of the alpha subclass at the time of species diversification or several more recent, independent transfers. Application of the phylogenetic analysis to DNA isolated from environmental samples demonstrated novel habitats for Azoarcus: in guts of termites and rice grown in Japan, nifH genes belonging to the authentic Azoarcus branch were detected. This is the first evidence suggesting the occurrence of Azoarcus spp. in a plant other than its originally described host, Kallar grass. Moreover, evidence for expression of nif genes inside grass roots was obtained by in situ hybridization studies with antisense nifH probes.Keywords
This publication has 29 references indexed in Scilit:
- Phylogenetic Analyses of a New Group of Denitrifiers Capable of Anaerobic Growth on Toluene and Description of Azoarcus tolulyticus sp. nov.International Journal of Systematic and Evolutionary Microbiology, 1995
- Taxonomic Position of Aromatic-Degrading Denitrifying Pseudomonad Strains K 172 and KB 740 and Their Description as New Members of the Genera Thauera, as Thauera aromatica sp. nov., and Azoarcus, as Azoarcus evansii sp. nov., Respectively, Members of the Beta Subclass of the ProteobacteriaInternational Journal of Systematic and Evolutionary Microbiology, 1995
- Two-membered mixed cultures of methanogenic and aerobic bacteria in O2-limited chemostatsJournal of General Microbiology, 1993
- Azoarcus gen. nov., Nitrogen-Fixing Proteobacteria Associated with Roots of Kallar Grass (Leptochloa fusca (L.) Kunth), and Description of Two Species, Azoarcus indigens sp. nov. and Azoarcus communis sp. nov.International Journal of Systematic and Evolutionary Microbiology, 1993
- Self-splicing introns in tRNA genes of widely divergent bacteriaNature, 1992
- Identification in situ and phylogeny of uncultured bacterial endosymbiontsNature, 1991
- Genetic diversity in Sargasso Sea bacterioplanktonNature, 1990
- Characterization of Herbaspirillum seropedicae gen. nov., sp. nov., a Root-Associated Nitrogen-Fixing BacteriumInternational Journal of Systematic and Evolutionary Microbiology, 1986
- Improved M13 phage cloning vectors and host strains: nucleotide sequences of the M13mpl8 and pUC19 vectorsGene, 1985
- Intestinal Microbiota of Termites and other Xylophagous InsectsAnnual Review of Microbiology, 1982