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1 April 2009 Grass Rhizosheaths: Associated Bacterial Communities and Potential for Nitrogen Fixation
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Rhizosheaths are structures composed of mucilage secreted from plants and adherent soil particles that form a cylinder around the root. Using scanning electron microscopy (SEM), we observed bacteria associated with rhizosheaths of the grasses Achnatherum hymenoides, Calamovilfa longifolia, Hesperostipa comata, and Pascopyrum smithii from a sand dune area in Harding County in northwestern South Dakota. The greatest numbers of bacteria, observed with SEM (529 mm-2), and the greatest number of culturable bacteria (9.9 × 107 CFU · g-1 or 5178 CFU · mm-2) were on rhizosheaths of C. longifolia. Rhizosheaths of all the grasses examined contained a higher density of bacteria than the surrounding soil. Nitrogen fixation, as assayed by reduction of acetylene to ethylene, was present in some rhizosheaths. Bacterial nifH gene sequences amplified from bacteria associated with rhizosheaths were most similar to those from Alcaligenes latus and Mesorhizobium loti.

© 2009
David Bergmann, Mike Zehfus, Linda Zierer, Brian Smith, and Mark Gabel "Grass Rhizosheaths: Associated Bacterial Communities and Potential for Nitrogen Fixation," Western North American Naturalist 69(1), 105-114, (1 April 2009).
Received: 8 June 2007; Accepted: 1 September 2008; Published: 1 April 2009

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