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Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Graham, Linda [1], Zulkifly, Sharizim [2], Hanshew, Alyssa [3], Young, Erica [4], Graham, Melissa [5], Graham, Michael [6], Piotrowski, Michael [7].

The epiphytic microbiota of the globally widespread macroalga Cladophora (Chlorophyta, Cladophorales).

The herbivore- and pathogen-resistant, filamentous green algal genus Cladophora KuÌtz. occurs as abundant populations along rocky marine and freshwater shorelines worldwide, commonly dominating periphyton communities. In eutrophic conditions, Cladophora can produce nuisance growths of societal concern. However, characteristics of rapid growth, persistence, acclimation to irradiance changes, phosphorus storage, and production of abundant lignin-free cellulose offer the potential for technological applications of Cladophora. In engineered systems Cladophora can remove excess mineral nutrients from wastewater effluents (thereby reducing eutrophication impacts) while also generating biofuel feedstocks (Hoover et al. 2011). The significant ecological role of Cladophora in providing high surface area habitat that supports a high functional and taxonomic diversity of epiphytic microfauna has labeled Cladophora as an ecological engineer. Dense and diverse epiphytic diatoms on Cladophora are hypothesized to influence lake silica cycling. We examined the hypothesis that Cladophora likewise supports a structurally and functionally diverse epiphytic bacterial microbiota having potential roles in materials cycling and mutualistic host-microbial interactions. We evaluated the microbiota of actively growing C. glomerata from hypereutrophic Lake Mendota, Dane, Co., WI, collected monthly during the 2011 growing season, by means of correlative SEM and fluorescence microscopy and Roche 454 pyrosequencing. Microscopy revealed the common occurrence of several distinctive prokaryotic morphotypes. 11,670 16S rRNA gene amplicons (200-600 bp long) were evaluated using RDP classifier to identify epiphytic bacteria to genus at the 80% level or species at the 96-97% level. Taxa identified were used to infer functional bacterial phenotypes. We found evidence for about 100 distinct bacterial genera or species, within 9 bacterial phyla representing diverse functional characteristics. We inferred that the normal epiphytic bacterial flora of Lake Mendota C. glomerata includes oxygenic and anoxygenic autotrophs, organisms that engage in diverse mineral redox reactions, many types of organic degraders including several cellulose-degraders, and predators. Some bacterial epiphytes identified have metabolic functions such as vitamin B12 production, nitrogen fixation,or methanotrophy that could imply mutualistic interactions with the Cladophora host. These results, together with global abundance, suggest that Cladophora-dominated periphyton plays important roles in aquatic C and N cycling. Finally, previous molecular sequencing-based analyses of nuisance beach drift Cladophora glomerata along western Lake Michigan accomplished by other workers had identified Escherichia coli and other potentially pathogenic enteric species. However our sequencing study suggested that in actively growing lentic Cladophora there was no evidence for the presence of such mammalian pathogens.

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1 - University Of Wisconsin, Botany Dept, 211 Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, USA
2 - Universiti Putra Malaysia, Biology, 43400 UPM Serdang, Selangor, Malaysia
3 - University of Wisconsin, Bacteriology, Madison, WI, 53706, USA
4 - University of Wisconsin-Milwaukee, Biological Sciences, Milwaukee, WI, 53211, USA
5 - University of Wisconsin, School of Veterinary Medicine, Madison, WI, 53706, USA
6 - Hologic, Inc., 502 South Rosa Road, Madison, WI, 53719, USA
7 - University of Wisconsin, Botany, Madison, WI, 53706, USA

epiphytic microbiota

Presentation Type: Poster:Posters for Topics
Session: P
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM
Number: PDB001
Abstract ID:317

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