Open AccessThree distinct clades of cultured heterocystous cyanobacteria constitute the dominant N 2 ‐fixing members of biological soil crusts of the Colorado Plateau, USA
Author(s) -
Yeager Chris M.,
Kornosky Jennifer L.,
Morgan Rachael E.,
Cain Elizabeth C.,
GarciaPichel Ferran,
Housman David C.,
Belnap Jayne,
Kuske Cheryl R.
Publication year - 2007
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.2006.00265.x
Subject(s) - biology , nostoc , clade , cyanobacteria , botany , plateau (mathematics) , diazotroph , 16s ribosomal rna , phylogenetics , nitrogen fixation , ecology , bacteria , gene , mathematical analysis , genetics , mathematics , biochemistry
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.