SS2.03 Phytoplankton Ecology Using Molecular Approach
Date: Thursday, June 13, 2002
Time: 4:30:00 PM
Location: Colwood
 
MannEL, Scripps Institution of Oceanography, La Jolla, USA, emann@ucsd.edu
Barbeau, K, A, Scripps Institution of Oceanography, La Jolla, USA, 
Butler, A, , University of CA, Santa Barbara, Santa Barbara, USA, 
Haygood, M, G, Scripps Institution of Oceanography, La Jolla, USA, 
 
THE PHYLOGENETIC DIVERSITY OF BACTERIA ASSOCIATED WITH TRICHODESMIUM COLONIES
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Trichodesmium are marine, colonial N2-fixing cyanobacteria that contribute significantly to new nitrogen pools in the tropical and subtropical oceans. N2 fixation by Trichodesmium can be iron limited, but little is known about the mechanisms by which this cyanobacteria acquires iron. Bacteria are closely associated with both fusiform (tuft) and radial (puff) Trichodesmium colonies. To date, these associated bacteria, but not Trichodesmium itself, have been shown to produce iron binding compunds or siderophores. We hypothesize that Trichodesmium may acquire iron by using siderophores synthesized by their associated bacteria. The first step in investigating this hypothesis is to identify and isolate these bacteria. Clone libraries of SSU rRNA genes from Trichodesmium colonies include sequences from the alpha, beta, and gamma subdivisions of Proteobacteria as well as members of the Cytophaga-Flavobacteria-Bacteroides lineage. The beta and gamma proteobacteria were associated almost exclusively with puffs, but a unique cluster of alpha proteobacteria SSU rRNA gene sequences were present in all of the Trichodesmium colonies examined. These bacteria may have a specific, mutualistic relationship with Trichodesmium.