Ecological, Phylogenetic and Taxonomic Remarks on Diazotrophs and Related Genera

摘要: Nitrogen-fixing organisms are very diverse prokaryotes that have been identified scattered in the phylogenetic trees reconstructed from comparative analysis of ribosomal RNA gene sequences (Martinez-Romero, 1985, Young, 1992). Although 16S rRNA gene-based phytogenies criticized and Universal Tree Life questioned (Pennisi, 1998), novel approaches proteome derived genomes 20 provide support to unrooted based on genes (Tekaia et al., 1999). However, final answer has not yet given this highly controversial field. A critical overview phylogenies compared other markers presented (Martinez-Romero Anyhow, it is clear nitrogen fixers found close relationship non fixers. Nitrogen may constitute clusters restricted distribution inside groups non-fixing bacteria as case Acetobacter diazotrophicus N-fixing species (Caballero-Mellado 1999; Fuentes-Ramirez al, volume) or Paenibacillus among aerobic endospore-forming Firmicutes (Achouak In Archea, Nfixation a general property methanogen group nif halophiles, but no sulfur dependent archaeobacteria. The Frankia actynomycetes includes atypical strains well an infective fixer isolate (Normand 1996); Rhizobium there fixers, nonsymbiotic (Segovia 1991), meaning fixation be easily lost some cases. loss fixing ability proposed explain occurring closely related bacteria.