Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation


Document Type


Degree Name

Master of Science (MS)


Department of Biology


Louie Wurch

Morgan Steffen

Pradeep Menon


Currently, there is a pernicious microbe in the genus Microcystis that is putting the world’s freshwater resources at risk. A member of the phylum Cyanobacteria, otherwise referred to as blue-green algae, Microcystis forms massive algal blooms in lakes and has the potential to produce a toxin, which does not only harm humans, but also pets, livestock, and aquatic life. As recently as 2016, in the city of Toledo, Ohio, nearly 1 million residents went without clean drinking water for an entire weekend due to one of these Microcystis blooms. However, Microcystis does not only bloom in Ohio. In fact, it has been reported on every continent in the world with the exception of Antarctica. Despite tremendous efforts invested into research, the exact factors leading to Microcystis blooms remain unsolved. Most studies have examined the role of abiotic, or nonliving, factors such as warm temperatures or nutrients from fertilizer runoff as being important drivers of these blooms. However, recent attention has shifted to the potential role of biotic factors. Microcystis blooms should not be thought of as being caused by one single species, but rather a complex assemblage of a variety of different types of bacteria and other microbes that interact with the algae in a variety of different ways. It is this perspective that has driven the hypotheses, methodology, and analyses of this thesis. A comprehensive literature review in chapter one puts my work in a broader context. I then characterize and describe the community structure associated with Microcystis in established cultures and compare that to the microbiomes of other cyanobacteria and eukaryotic algae in my second chapter. Finally, in chapter three, I analyzed the effects of heterotrophic bacteria isolated from natural Microcystis blooms in Lake Erie (USA) and Lake Tai (China) on the growth and physiology of Microcystis aeruginosa through detailed co-cultures. The data and analyses contained herein are a critical next-step in attempting to understand the drivers behind Microcystisblooms as we work toward better protecting our freshwater resources.



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