Date Approved

2023

Degree Type

Open Access Senior Honors Thesis

Department or School

Biology

First Advisor

Michael G. Angell, Ph.D.

Second Advisor

Aaron H. Liepman, Ph.D.

Third Advisor

Natalie Dove, Ph.D.

Abstract

Increasing global temperatures and nutrient availability from anthropogenic sources have contributed to climate change and pollution in waterways. Environmental changes have promoted annual harmful algal blooms (HABs), which have the potential to lead to conditions that negatively affect aquatic ecosystems and organisms that depend on them. HABs can impact water quality through the release of soluble toxins (e.g., microcystin), produced by cyanobacteria that can bypass standard drinking water processing protocols. It has been suggested that viral infections of cyanobacteria may contribute to increased production and release of microcystins. In this project, two hypotheses were assessed: 1) virus-mediated lysis releases toxins from a filterable intracellular form within Microcystis aeruginosa cells to an extracellular soluble toxin, and 2) viral infection induces a greater accumulation of intracellular toxins when compared to the non-infected controls. To evaluate these hypotheses, laboratory cultures of M. aeruginosa NIES 298 were infected with cyanophage Ma-LMM01, and levels of microcystins were quantified using ADDA-ELISA. An additional analysis included water sampling for viral abundance and microcystin concentration in Ford Lake, Ypsilanti MI. ADDA-assay revealed that viral infection of M. aeruginosa is correlated with higher accumulations of extracellular and intracellular microcystins. This research contributes to an understanding of the impacts of phagehost interactions on microcystin production and release into the environment.

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