THE UNIVERSITY OF TENNESSEE
AQUATIC MICROBIAL ECOLOGY RESEARCH GROUP
Steven W. Wilhelm - Professor OF Microbiology
Office: 865-974-0665 Labs: 865-974-0682 or 865-974-4014
CURRENTLY FUNDED RESEARCH PROJECTS
Development of a tractable genetic system for Aureococcus anophagefferens.
Funding Source: The Gordon & Betty Moore Foundation
PI. SW Wilhelm. coPIs ER Zinser, T Sparer, T Reynolds and WH Wilson.
Aureococcus anophagefferens, the cause of Brown Tides, persists in coastal regions globally in what many considered hostile environments (i.e., turbid, enriched in nutrient and trace metal waste, etc.) at densities of greater than 109 cells L-1. This organism has a highly mosaic genome, indicative of frequent genomic modifications. Along with suggestions that Aureococcus undergoes natural transformation, members of these populations are regularly infected by a giant virus (AaV) that is enriched with repeats believed to be active in genomic shuffling and frequent gene exchange between the virus and its host. Indeed, exchange has also occurred between AaV and other non-host organisms (i.e., bacteria and other algae) and implies a natural recombination mechanism with A. anophagefferens as the intermediate. We will develop a genetic system for Aureococcus that can serve to further our understanding of this algae’s ecology and evolution as well provide potential for biotechnological advances. A series of approaches, including the use of the AaV and putative repeat regions that may encode promoters, will be employed in the transformation of Aureococcus. Along with direct transduction using modified AaV, we propose to take advantage of tools developed for the transformation of other algae (e.g., Chlorella, Nannochloropsis, Emiliania huxleyi) and other single-celled eukaryotes.
Award Abstract #1451528.
Collaborative Research: an integrated
approach to understanding the function of the potent hepatotoxin microcystin
in the growth & ecology of Microcystis
Funding source: NSF Division of Integrative Organismal Systems
PI SW Wilhelm. coPIs ER Zinser, SR Campagna, JM DeBruyn, EM Fozo and GL Boyer
Blooms of toxic photosynthetic bacteria (cyanobacteria)
are occurring globally with expanding frequency, duration and intensity in
lakes, reservoirs and river systems. Most recently blooms of the toxic
cyanobacterium Microcystis shut down the water supply of the city of Toledo,
OH for a weekend in August of 2014. While the scientific community has
developed a solid understanding of the factors that contribute to the blooms
of Microcystis, previous research has not explained why cells make the
hepato- (liver) toxin microcystin. As a potent inhibitor of a key class of
enzymes - protein phosphatases - microcystin might play important roles
inside Microcystis cells, and once released, inside the cells of other
(target) organisms. This project will use advanced tools in molecular
biology (RNA sequencing), microbial genetics, the quantification of small
metabolites (metabolomics) and enzyme analyses to understand how the
presence of microcystin shapes the activity of both the cells that make the
compound and the community of microorganisms around them. Experiments in the
laboratory will be complemented by field surveys of bloom events across
naturally occurring toxin gradients - areas of historically high and low
concentrations of toxin during the summer bloom season. State-of-the-art
statistical analyses combined with these advanced scientific approaches will
transform the understanding of why these cyanobacteria make this toxic
compound. Understanding of the biological functions of the microcystin, will
lead to better stewardship of a valuable natural resource: potable water.
The total research effort will train students, including those from
underrepresented groups, and broadly disseminate information to the public,
systems managers and the scientific community. A significant component will
feed into state-associated, in-class 4H training that will expose as many as
200,000 students to cyanobacteria as a model system to examine complex
Award Abstract #1240870.
Research: Anthropogenic nutrient input drives genetic, functional and
taxonomic biodiversity in hypereutrophic Lake Taihu, China.
Funding Source: NSF DEB (Dimensions of Biodiversity program).
PI HW Paerl. coPIs SW Wilhelm, W Gardner, F Hellweger. Collaborator GL Boyer.
Human activities have dramatically increased nitrogen inputs into many
rivers and lakes, causing algal blooms that threaten economic and
recreational uses of those waters. Lake Taihu, the third largest lake in
China, experiences damaging blooms of toxic cyanobacteria as a result of
excessive nutrient inputs. The identities, nitrogen processing capabilities,
and activities of microbial communities in Lake Taihu will be examined to
determine if nitrogen processing can be predicted from knowledge of the
identity and genetic makeup of those communities. Various components of the
nitrogen cycle will be measured and linked to representative molecular
markers which, coupled with high throughput genetic sequencing, will provide
a genetic database of nitrogen-cycling processes in freshwater ecosystems. A
goal of the project will be to link microbial taxonomic, genetic, and
functional data in a model that can predict how reduction of nutrient inputs
will affect toxic cyanobacterial blooms.