Date of Award

Fall 2021

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

John Ferry

Abstract

Cyanobacteria has existed on the planet for over 3 billion years, and as technology, science, and industry have allowed us to shape our world, these changes have caused a proliferation of biomass. Higher carbon dioxide levels in the atmosphere, warmer temperatures, and rapid increases in the nutrient cycle have created excellent growing conditions for cyanobacteria, making them endemic in fresh waters throughout the world. The work in this dissertation was directed towards the secondary metabolites produced by cyanobacteria and other surrounding microbes and understanding their concentrations and release in natural systems. Analytical methods were developed for the extraction and quantification of the Lyngbya wollei toxins produced by Microseira wollei and found in a bloom occurring in Lake Wateree, SC. In collaboration with a local citizen science group, the bloom in this lake was monitored over the course of nearly two years, including toxin measurements as well as other water quality parameters. A model was adapted and used as a diagnostic to identify the main driver of the bloom, legacy sedimentary phosphorus. An extension of this model was also developed to estimate the potential toxin burden in biomass given a sediment phosphorus concentration. Although toxin was readily detected within the cells, the release mechanism was unclear. A lake being treated with pesticide to control a bloom of Microseira wollei was used as a natural laboratory to examine the change in toxin withing the biomass during that treatment. A significant decrease in intracellular toxin was observed in the field, but when experiments with a manifold of pesticides were performed in the laboratory, there was no increase in water column toxin concentration. Further experiments demonstrated that toxin is sequestered within the cells even under conditions that cause death and can be released with the addition of protons through acidification.

N-acyl-homoserine lactones are a group of quorum sensing molecules that control a variety of community behaviors, and can be difficult to detect in natural samples due to their transient nature. Liquid chromatography mass spectrometry methods were developed for the individual molecular detection of these signals and tested with lab grown and natural cultures.

Available for download on Thursday, December 15, 2022

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