Didymosphenia geminata: Induction
of Exopolymer Synthesis in the Nuisance Diatom Didymosphenia geminata
Results in Significant Environmental Impact
(Collaborators: David Domozych & Sarah Spaulding) |
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In recent years, streams in New Zealand, North America, Europe, and Asia
have been disrupted by unprecedented blooms of the freshwater diatom
Didymosphenia geminata. (Didymo). Didymo blooms can cover up to 100% of
surfaces with mats of thickness greater than 20 cm, greatly altering
physical and biological conditions within streams. These mats are
primarily composed of extracellular stalks exuded by D. geminata
through an apical porefield. When cells divide within a mat, the stalk
bifurcates, the end result of which is an overall branched structure
with stalks intercalating and coalescing to form an aggregate “woven
fabric” that trap algae, macroinvertebrates, detritus and other stream
debris and which, at a macro scale, resemble raw sewage and are quite
resistant to degradation. As a first step toward determining what has
been “turned on” at the molecular level to result in such massive
production of stalks in recent nuisance blooms worldwide, we are
investigating details of stalk formation, structure and chemistry.
Initial indications are that the sulfated xylogalactan dominated stalks
of D. geminata are very similar to those of the stalked diatoms
Cymbella mexicana, Cymbella cistula, and Gomphonema olivaceum. Increased
stalk production by these species could result in massive disturbance of
freshwater flowing water ecosystems worldwide.
Funding
Source: BioSecurity New Zealand Link: http://www.biosecurity.govt.nz/didymo Collaborators: David Domozych, D.S. Biology Department
Skidmore College, Saratoga Springs, New York
Sarah Spaulding US Geological Survey & EPA Region 8
Boulder, Colorado
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