Digital Commons Network^™

Understanding Excitation Energy Quenching In Isia, Hui-Yuan Steven Chen

McKelvey School of Engineering Theses & Dissertations

Cyanobacteria are photoautotrophic organisms that contribute a significant amount of global primary productivity. They are found in freshwater, marine and even some extremely severe environments. Among those environments, iron deficiency is one of the most common stress conditions in cyanobacterial habitats. To survive, cyanobacteria have evolved and developed several strategies to alleviate the damage caused by iron deficiency.

Iron stress-inducible protein (IsiA) is a chlorophyll-binding membrane protein found in cyanobacteria grown in iron-deficient conditions. During the past decades, considerable effort has been put on understanding how IsiA functions to help cyanobacteria survive iron deficiency. It has been reported that IsiA …

Diverse Far-Red Light Utilization Strategies In Cyanobacteria And Algae, Benjamin Martin Wolf

Arts & Sciences Electronic Theses and Dissertations

In their natural environments, photosynthetic organisms are often exposed to widely varied light environments. Species adapted to shade light, often found growing in lower layers of photosynthetic biofilms, must survive on filtered light alone. Filtered light is highly enriched in far-red wavelengths, which are normally unavailable for photosynthetic energy production in most oxygenic phototrophs. To overcome light limitations in filtered light environments, some species of algae and cyanobacteria utilize specialized photosynthetic pigments and antenna systems to harvest these far-red wavelengths. By sampling the natural environment and using custom-built far-red light growth chambers, I have isolated several species of oxygenic phototrophs …

Metabolic Engineering Of Cyanobacteria For Production Of Chemicals, Po-Cheng Lin

McKelvey School of Engineering Theses & Dissertations

Concerns over the impact of climate change caused by CO2 emission have driven the research and development of renewable energies. Microbial production of chemicals is being viewed as a feasible approach to reduce the use of fossil fuels and minimize the impact of climate change. With recent advances in synthetic biology, microorganisms can be engineered to synthesize petroleum-based chemicals and plant-derived compounds. Cyanobacteria are photosynthetic prokaryotes that use only sunlight, CO2, and trace minerals for growth. Compared to other microbial hosts, cyanobacteria are attractive platforms for sustainable bioproduction, because they can directly convert CO2 into products. However, the major challenge …

Metabolic Engineering Of Cyanobacteria For Production Of Chemicals, Po-Cheng Lin

McKelvey School of Engineering Theses & Dissertations

Concerns over the impact of climate change caused by CO2 emission have driven the research and development of renewable energies. Microbial production of chemicals is being viewed as a feasible approach to reduce the use of fossil fuels and minimize the impact of climate change. With recent advances in synthetic biology, microorganisms can be engineered to synthesize petroleum-based chemicals and plant-derived compounds. Cyanobacteria are photosynthetic prokaryotes that use only sunlight, CO2, and trace minerals for growth. Compared to other microbial hosts, cyanobacteria are attractive platforms for sustainable bioproduction, because they can directly convert CO2 into products. However, the major challenge …

Building On Nature: Spectroscopic Studies Of Photosynthesis-Inspired Pigments, Fused Light Harvesting Proteins, And Bacterial Reaction Center Mutants, Kaitlyn Faries

Arts & Sciences Electronic Theses and Dissertations

Photosynthesis is the dominant form of solar energy conversion on the planet, making it critical to understand the fundamentals of the process in order to effectively mimic and improve upon it for human energy needs. The initial stages of photosynthesis include light harvesting and chemical conversion of that harvested energy via electron transport, with both of these stages relying on pigments (or chromophores) such as chlorophyll and specific protein architectures for the processes. In this work, the fundamental underpinnings of photosynthetic light harvesting and electron transport are explored via spectroscopy of various photosynthetic systems with altered natural pigments and proteins. …

Investigating The Life-Cycle Of Photosystem Ii Using Mass Spectrometry, Daniel Avram Weisz

Arts & Sciences Electronic Theses and Dissertations

Photosystem II (PSII) is a protein complex found embedded in the thylakoid membranes of all organisms that perform oxygenic photosynthesis. PSII converts sunlight into chemical energy, filling our atmosphere with molecular oxygen in the process and supporting nearly all life on Earth. PSII undergoes frequent light-induced damage as an unavoidable result of the electron transfer reactions it catalyzes. When damaged, PSII is disassembled, repaired, and reassembled in an intricate, tightly regulated process. The structure and mechanism of function of active PSII are relatively well-understood, due to the available crystal structures of the active complex and many years of biochemical and …

Use Of Proteomics To Probe Dynamic Changes In Cyanobacteria, Amelia Yen Nguyen

Arts & Sciences Electronic Theses and Dissertations

Cyanobacteria are unicellular photosynthetic microorganisms that capture and convert light energy to chemical energy, which is the precursor for feed, fuel, and food. These oxygenic phototrophs appear blue-green in color due to the blue bilin pigments in their phycobilisomes and green chlorophyll pigments in their photosystems. They also have diverse morphologies, and thrive in terrestrial, marine water, fresh water, as well as extreme environments. Cyanobacteria have developed a number of protective mechanisms and adaptive responses that allow the photosynthetic process to operate optimally under diverse and extreme conditions. Prolonged deprivation of essential nutrients, such as nitrogen and sulfur, commonly found …

Structure And Function Of Cytochrome Containing Electron Transport Chain Proteins From Anoxygenic Photosynthetic Bacteria, Erica Lois-Wunderlich Majumder

Arts & Sciences Electronic Theses and Dissertations

This dissertation examines the structure and function of photosynthetic proteins that contain c-type heme cofactors that function in the electron transport chains of anaerobic phototrophic bacteria. The diversity and range of these cytochromes proteins was explored. Then, individual proteins were studied in detail. The diheme cytochrome c from Heliobacteria modesticaldum was studied using hydrogen deuterium exchange mass spectrometry and homology modeling. A structural model of the protein and a mechanism for the cytochrome bc complex was proposed. Next, the monoheme cytochrome c subunit from the Alternative Complex III from the Filamentous Anoxygenic Phototrophs was studied using biochemistry and found to …

Light-Harvesting, Redox Control, And Biomimicry Of The Photosynthetic Antennas Of Green Sulfur Bacteria, Gregory Scott Orf

Arts & Sciences Electronic Theses and Dissertations

The green sulfur bacteria (class Chlorobea) are obligately anaerobic photoautotrophic prokaryotes. Members of this bacterial class are found in anoxic, sulfur- or iron-rich environments such as hydrothermal vents and hot springs. These bacteria are champions of lowlight adaptation, with some species being able to thrive photosynthetically on less than eight photons hr-1 per pigment. We have studied the two photosynthetic antenna complexes from these organisms that are responsible for light capture: the chlorosome and the Fenna-Matthews-Olson (FMO) protein.

In regards to the chlorosome, we studied, using steady-state and time-resolved spectroscopic methods, the effect of incorporation of an expected, but as-yet-undiscovered-in-nature, …

The Physiological Effects Of Phycobilisome Antenna Modification On The Cyanobacterium Synechocystis Sp. Pcc 6803, Lawrence Edward Page

All Theses and Dissertations (ETDs)

Phycobilisomes are the large, membrane extrinsic light harvesting antenna of cyanobacteria. They function to absorb light energy and deliver it efficiently to the photosystems, thereby increasing photosynthetic light absorption. Wild type phycobilisomes in the model organism Synechocystis sp. PCC 6803: Synechocystis 6803) consist of a tricylindrical core from which six rods radiate. The colored phycobiliproteins are held together by colorless linker polypeptides.

Several phycobilisome truncation mutants have been generated in Synechocystis 6803. The first, CB, has truncated phycobilisome rods; the second, CK, has only the phycobilisome core; and the third, PAL, has no phycobilisomes at all. Together, these mutants construct …

Redox Homeostasis In Cyanobacteria, Jeffrey Cameron

All Theses and Dissertations (ETDs)

Oxygenic photosynthetic organisms utilize high-energy electron transfer chains comprised of redox active intermediates and light harvesting complexes. While oxygen is a necessary byproduct of water oxidation and the source of photosynthetic electrons, its presence is also dangerous because leakage of electrons and excitation energy can interact with molecular oxygen to generate reactive oxygen species: ROS). Elaborate antioxidant networks and redox buffering systems have evolved to protect photosynthetic organisms from the threat of ROS. Glutathione: GSH) is a multifunctional molecule that is involved in core metabolism, detoxification of xenobiotics and in maintenance of cellular redox poise. The ubiquitous nature of glutathione …