title: Three distinct clades of cultured heterocystous cyanobacteria constitute the dominant N2-fixing members of biological soil crusts of the Colorado Plateau, USA.
abstract: The identity of the numerically dominant N(2)-fixing bacteria in biological soil crusts of the Colorado Plateau region and two outlying areas was determined using multiple approaches, to link the environmental diversity of nifH gene sequences to cultured bacterial isolates from the regions. Of the nifH sequence-types detected in soil crusts of the Colorado Plateau, 89% (421/473) were most closely related to nifH signature sequences from cyanobacteria of the order Nostocales. N(2)-fixing cyanobacterial strains were cultured from crusts and their morphotypes, 16S rRNA gene and nifH gene sequences were characterized. The numerically dominant diazotrophs in the Colorado Plateau crusts fell within three clades of heterocystous cyanobacteria. Two clades are well-represented by phylogenetically and morphologically coherent strains, corresponding to the descriptions of Nostoc commune and Scytonema hyalinum, which are widely recognized as important N(2)-fixing components of soil crusts. A third, previously-overlooked clade was represented by a phylogenetically coherent but morphologically diverse group of strains that encompass the morphogenera Tolypothrix and Spirirestis. Many of the strains in each of these groups contained at least two nifH copies that represent different clusters in the nifH environmental survey.
authors: Biosciences Division M888, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors: Chris M
authors: CM
authors: Yeager
authors: Jennifer L
authors: JL
authors: Kornosky
authors: Rachael E
authors: RE
authors: Morgan
authors: Elizabeth C
authors: EC
authors: Cain
authors: Ferran
authors: F
authors: Garcia-Pichel
authors: David C
authors: DC
authors: Housman
authors: Jayne
authors: J
authors: Belnap
authors: Cheryl R
authors: CR
authors: Kuske
mesh_terms: D003120:Colorado; D000458:Cyanobacteria / Q000145:classification* / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D017753:Ecosystem; D020459:Genes, rRNA; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation; D046937:Nostoc / Q000145:classification / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C029130:nitrogenase reductase