This work supports the production of food, fuel, and other bio-based products from single-celled organisms, or organisms grown in suspension, with the goal of reducing our environmental impact by minimizing our dependence on fossil fuels and resource intensive agriculture. I address three major bottlenecks currently limiting the bioeconomy. Biological photosynthesis, which is inefficient at converting solar energy into biomass, limits food production as well as many downstream processes that rely on plant products, like fermentation which relies on sugar. Our artificial photosynthetic technology addresses this by eliminating the need for biological photosynthesis in food production. Acetate produced from carbon dioxide and electricity, through electrochemical catalysis, is used to cultivate organisms heterotrophically, for an overall process that is substantially more solar-to-biomass energy-conversion efficient than biological photosynthesis. Typically, heterotrophic growth is reliant upon biological photosynthesis for a source of carbon and energy, including sugar from plants or petroleum, a product of ancient photosynthesis. To confront this, I explored the potential of acetate as a carbon and energy source for the cultivation of plant cell cultures. By establishing the current limitations, investigating the metabolism, and quantifying expression of important genes, I set the groundwork to eventually cultivate plant cell cultures independent from industrial agriculture, perhaps within our artificial photosynthetic system. The third bottleneck addressed in this work is plant and algal lipid metabolism, which is yet to be fully understood and limits the production of fuel and other lipid-based products. I used a high-throughput, forward genetic, genome-wide mutant screen in a model green algal species to identify genes important for lipid accumulation in response to nitrogen deprivation. The three projects described in this thesis aim to address the sustainable production of important products we rely on and use daily. This work can be built upon to innovate and move away from fossil fuels and inefficient industrial agricultural practices, for the benefit of our planet and future generations.

The survival of coral reefs in the face of environmental stress is dependent on understanding the cellular and molecular mechanisms that govern Cnidaria-Symbiodiniaceae symbiosis. However, the relative genetic intractability of the Symbiodiniaceae symbiont has led to a bottleneck in the availability of Symbiodinaceae mutants that can be applied towards this purpose. This work describes a protocol for the utilization of UV mutagenesis and downstream screening process for the discovery of Symbiodiniaceae mutants with phenotypes of interest and their application. Algal photosynthesis plays an important role in the symbiosis, assisting in the spread of symbionts to host cells throughout the host gastrodermal tissue, as well as providing fixed carbon to the host. This role makes it of interest for investigation. Symbiodiniaceae mutants lacking the ability to perform photosynthesis were generated following the protocol and applied to in hospite conditions across multiple cnidarian species. The results show that photosynthetic activity is not required for the establishment of algal association, suggesting different criteria are required for association within the host cell. Furthermore, the rate of algal division has been shown to differ among strains of Symbiodiniaceae, leading to differences in the symbiosis phenotype. Low algal division rate has been hypothesized to confer temperature stress, warranting further investigation into this phenotype. As such, a mutant with a suppressed division rate in mixotrophic culture conditions was also discovered and applied to answer questions about the symbiosis. Reduced algal division rate was observed in hospite, as well as a reduced final algal density and animal size compared to the original Symbiodiniaceae strain. While these initial investigations into the role of photosynthesis and algal division rate have provided insight into these aspects of the symbiosis, further work can be performed with these mutants, particularly work pertaining to temperature stress resistance. The successful creation and application of these mutants showcase the utility of UV mutagenesis and screening processes as a valid approach for the future discovery of Symbiodiniaceae mutants with other phenotypes of interest.