Assistant Professor of Biology 

B.S. - Iowa State University

Ph. D. - University of Tennessee

Office Hours

Research Interests:

Environmental microbiology, Cyanobacterial genomics

Microorganisms are key members of aquatic ecosystems, largely due to their critical role in biogeochemical processes. In our laboratory, we try to understand the interactions of key members of aquatic microbial communities with other organisms and the surrounding environment. Specifically, we use a combination of molecular and genomic techniques to study microbial communities associated with blooms of toxic cyanobacteria.

Cyanobacterial harmful algal blooms (or cHABs) plague aquatic ecosystems around the world. Toxins associated with bloom events can devastate local ecology, impact revenues from tourism and fishery industries, and limit the supply of potable water to surrounding communities. Members of the genus Microcystis are globally distributed and are often dominant members of bloom communities. The success of these organisms in the environment is known to be influenced by factors such as nutrient availability and temperature. However, the suite of factors that drive the dominance of Microcystis and other toxic cyanobacteria have yet to be identified. Currently, I am interested in the role of specific nutrients in shaping bloom community structure and the genomic architecture of individual community members.

There are opportunities in my lab for students interested in microbial ecology and microbial genomics. Using a combination of techniques from molecular biology, microbiology, genomics, and biochemistry, students may participate in laboratory and field-based projects to test the role of nutrients and other environmental factors in driving dominance of various species of the cHAB organisms in aquatic systems.


Harke, M.J., Steffen, M.M.*, Gobler, C.J., Otten, T.G., Wilhelm, S.W., Wood, S.A., Paerl, H.W. 2016. A review of the global ecology, genomics, and biogeography of the toxic cyanobacterium, Microcystis. Harmful Algae. 54 (2016): 4-20. *Corresponding author to invited publication in special issue of Harmful Algae*

Steffen, M.M., Belisle, B.S., Watson, S.B., Boyer, G.L., Bourbonniere, R.A., Wilhelm, S.W. 2015. Metatranscriptomic evidence for co-occurring top-down and bottom-up controls on toxic cyanobacterial communities. Applied and Environmental Microbiology. 81(9): 3268-3276.

Steffen, M.M., Dearth, S.P., Campagna, S.R., Boyer, G.L., Wilhelm, S.W. 2014. Nutrient chemistry  shapes cellular physiology and evolutionary trajectory in MicrocystisISMEJ. 8: 2080-2092.

Steffen, M.M., Zhu, Z., McKay, R.M., Wilhelm, S.W., Bullerjahn, G.S. 2014. Taxonomic assessment of a toxic cyanobacteria shift during the 2010 bloom in hypereutrophic Grand Lake St. Marys (Ohio, USA). Harmful Algae. 33: 12-18.

Steffen, M.M., Belisle, B.S., Waston, S., Boyer, G.L., Wilhelm, S.W. 2014. Review: Status, causes, and controls of cyanobacterial blooms in Lake Erie. Journal of Great Lakes Research. 40: 215-224.

Steffen, M.M., Li, Z., Effler, T.C., Hauser, L.J., Boyer, G.L., Wilhelm, S.W. 2012. Comparative metagenomics of toxic freshwater cyanobacteria bloom communities on two continents. PLoS ONE. 7(8).

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