Poster: Plant Pathogen/Symbiont Interactions
Abs #
724: Endophytic nitrogen fixation in European beachgrass (Ammophila arenaria)
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Presenter: |
Dalton, David A., david.dalton@reed.edu |
Authors | Dalton, David A. (A) Fusaro, Suzanne (A) Kramer, Sasha (A) Azios, Nico (A) | | Affiliations: |
(A): Reed College
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Ammophila arenaria(European beachgrass) is a prolific, dune-stabilizing grass that has been widely planted along the coast of western North America. This species is notable for its aggressive success on bare sand and for its displacement of more desirable, native plants. Our data show that European beachgrass is capable of nitrogen fixation through the presence of endophytic bacteria. Rhizomes and stems displayed modest acetylene reduction activity (mean of 0.76 nmol C2H4 g-1FW h-1, max. of 24.8 nmol C2H4 g-1FW h-1). Numerous bacteria (>107 cfu g-1FW) were isolated from surface-sterilized plant tissue and cultured on N-free media. Among the bacteria identified by sequencing of 16S rRNA genes were: Agrobacterium radiobacter, Agrobacterium rubi, Allorhizobium undicola, Burkholderia sp., Enterobacter agglomerans, Nevskia sp., Ochrobactrum sp., Pantoea sp., Pseudomonas spp., Roseomonas genomospecies, Sphingomonas sp., Stenotrophomonas maltophila, and Xanthomonas campestris celebensis. All isolates were screened by PCR for the presence of nifH and nifD genes. Positive results were obtained only for Burkholderia. This isolate also reduced acetylene in culture with a maximum activity at 3 to 5% O2. Immunostaining with antibodies against nitrogenase revealed labeling within the cell walls of rhizomes and stems of A. arenaria as well as Elymus mollis (American dune grass, from the Oregon coast) and Uniola paniculata (sea oats, from the North Carolina coast) thus suggesting that nitrogen fixation may be a common trait in grasses found in coastal sand habitats. We hypothesize that these grass species harbor low to moderate populations of nitrogen-fixing bacteria within the plant cell walls in complex microbial communities that are dominated by non-fixing bacteria.
