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There is an ever-increasing need in the world to develop a source of fuel that is clean, renewable and feasible in terms of production and implementation. Hydrogen gas presents a possible solution to these energy needs, particularly if given a way to produce hydrogen gas efficiently. Biological hydrogen (biohydrogen) production

There is an ever-increasing need in the world to develop a source of fuel that is clean, renewable and feasible in terms of production and implementation. Hydrogen gas presents a possible solution to these energy needs, particularly if given a way to produce hydrogen gas efficiently. Biological hydrogen (biohydrogen) production presents a potential way to do just this. It is known that hydrogenases are active in wild-type algal photosynthesis pathways but are only active in anoxic environments, where they serve as electron sinks and compete poorly for electrons from photosystem I. To circumvent these issues, a psaC-hydA1 fusion gene was designed and incorporated into a plasmid that was then used to transform hydrogenase-free Chlamydomonas reinhardtii mutants. Results obtained suggest that the psaC-hydA1 gene completely replaced the wild-type psaC gene in the chloroplast genome and the fusion was expressed in the algal cells. Western blotting verified the presence of the HydA1-PsaC fusion proteins in the transformed cells, P700 photobleaching suggested the normal assembly of FA/FB clusters in PsaC-HydA1, and PSII fluorescence data suggested that HydA1 protein limited photosynthetic electron transport flow in the fusion. Hydrogen production was measured in dark, high light, and under maximal reducing conditions. In all conditions, the wild-type algal strain (with a normal PsaC protein) exhibited higher rates of hydrogen production in the light over 2 hours than the WT strain, though both strains produced similar rates in the dark.
ContributorsSmith, Alec (Author) / Redding, Kevin (Thesis director) / Jones, Anne (Committee member) / Vermaas, Willem (Committee member) / School of Molecular Sciences (Contributor) / Sanford School of Social and Family Dynamics (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
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Heliobacteria are an anaerobic phototroph that require carbon sources such as pyruvate, <br/>lactate, or acetate for growth (Sattley, et. al. 2008). They are known for having one of the <br/>simplest phototrophic systems, the central component of which is a Type I reaction center (RC) <br/>that pumps protons to generate the

Heliobacteria are an anaerobic phototroph that require carbon sources such as pyruvate, <br/>lactate, or acetate for growth (Sattley, et. al. 2008). They are known for having one of the <br/>simplest phototrophic systems, the central component of which is a Type I reaction center (RC) <br/>that pumps protons to generate the electrochemical gradient for making ATP. Heliobacteria <br/>preform cyclic electron flow (CEF) with the RC in the light but can also grow chemotropically in <br/>the dark. Many anaerobes like heliobacteria, such as other members of the class Clostridia, <br/>possess the capability to produce hydrogen via a hydrogenase enzyme in the cell, as protons can <br/>serve as an electron acceptor in anaerobic metabolism. However, the species of heliobacteria <br/>studied here, H. modesticaldum have been seen to produce hydrogen via their nitrogenase <br/>enzyme but not when this enzyme is inactive. This study aimed to investigate if the reason for <br/>their lack of hydrogen production was due to a lack of an active hydrogenase enzyme, possibly <br/>indicating that the genes required for activity were lost by an H. modesticaldum ancestor. This <br/>was done by introducing genes encoding a clostridial [FeFe] hydrogenase from C. thermocellum<br/>via conjugation and measuring hydrogen production in the transformant cells. Transformant cells <br/>produced hydrogen and cells without the genes did not, meaning that the heliobacteria ferredoxin <br/>was capable of donating electrons to the foreign hydrogenase to make hydrogen. Because the <br/>[FeFe] hydrogenase must receive electrons from the cytosolic ferredoxin, it was hypothesized <br/>that hydrogen production in heliobacteria could be used to probe the redox state of the ferredoxin <br/>pool in conditions of varying electron availability. Results of this study showed that hydrogen <br/>production was affected by electron availability variations due to varying pyruvate <br/>concentrations in the media, light vs dark environment, use acetate as a carbon source, and being <br/>provided external electron donors. Hydrogen production, therefore, was predicted to be an <br/>effective indicator of electron availability in the reduced ferredoxin pool.

ContributorsVilaboy, Tatum (Author) / Redding, Kevin (Thesis director) / Ghirlanda, Giovanna (Committee member) / School of Life Sciences (Contributor) / School of Criminology and Criminal Justice (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Coral reefs are diverse marine ecosystems, where reef building corals provide both the structure of the habitat as well as the primary production through their symbiotic algae, and alongside algae living on the reef itself, are the basis of the food web of the reef. In this way, coral reefs

Coral reefs are diverse marine ecosystems, where reef building corals provide both the structure of the habitat as well as the primary production through their symbiotic algae, and alongside algae living on the reef itself, are the basis of the food web of the reef. In this way, coral reefs are the ocean's "forests" and are estimated to support 25% of all marine species. However, due to the large size of a coral reef, the relative inaccessibility and the reliance on in situ surveying methods, our current understanding of reefs is spatially limited. Understanding coral reefs from a more spatially complete perspective will offer insight into the ecological factors that contribute to coral reef vitality. This has become a priority in recent years due to the rapid decline of coral reefs caused by mass bleaching. Despite this urgency, being able to assess the entirety of a coral reef is physically difficult and this obstacle has not yet been overcome. However, similar difficulties have been addressed in terrestrial ecosystems by using remote sensing methods, which apply hyperspectral imaging to assess large areas of primary producers at high spatial resolutions. Adapting this method of remote spectral sensing to assess coral reefs has been suggested, but in order to quantify primary production via hyper spectral imaging, light-use efficiencies (LUEs) of coral reef communities need to be known. LUEs are estimations of the rate of carbon fixation compared to incident absorbed light. Here, I experimentally determine LUEs and report on several parameters related to LUE, namely net productivity, respiration, and light absorbance for the main primary producers in coral reefs surrounding Bermuda, which consist of algae and coral communities. The derived LUE values fall within typical ranges for LUEs of terrestrial ecosystems, with LUE values for coral averaging 0.022 ± 0.002 mol O2 mol photons-1 day-1 at a water flow rate of 17.5 ± 2 cm s^(-1) and 0.049 ± 0.011 mol O2 mol photons-1 day-1 at a flow rate of 32 ± 4 cm s^(-1) LUE values for algae averaged 0.0335 ± 0.0048 mol O2 mol photons-1 day-1 at a flow rate of 17.5 ± 2 cm s^(-1). These values allow insight into coral reef productivity and opens the door for future remote sensing applications.
ContributorsFlesher, David A (Author) / Neuer, Susanne (Thesis director) / Redding, Kevin (Committee member) / School of Molecular Sciences (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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The oxygen sensitivity of hydrogenase is a large barrier in maximizing the efficiency of algal hydrogen production, despite recent efforts aimed at rewiring photosynthesis. This project focuses on the role of photosystem II (PSII) in extended hydrogen production by cells expressing the PSI-HydA1 chimera, with the goal of optimizing continuous

The oxygen sensitivity of hydrogenase is a large barrier in maximizing the efficiency of algal hydrogen production, despite recent efforts aimed at rewiring photosynthesis. This project focuses on the role of photosystem II (PSII) in extended hydrogen production by cells expressing the PSI-HydA1 chimera, with the goal of optimizing continuous production of photobiohydrogen in the green alga, Chlamydomonas reinhardtii. Experiments utilizing an artificial PSII electron
Therefore, it can be concluded that downstream processes are limiting the electron flow to the hydrogenase. It was also shown that the use of a PSII inhibitor, 3-(3,4-dichlorophenyl)-1,1- dimethylurea (DCMU), at sub-saturating concentrations under light exposure during growth temporarily improves the duration of the H2 evolution phase. The maximal hydrogen production rate was found to be approximately 32 nmol h-1 (µg Chl)-1. Although downregulation of PSII activity with DCMU improves the long-term hydrogen production, future experiments must be focused on improving oxygen tolerance of the hydrogenase as a means for higher hydrogen yields.
ContributorsO'Boyle, Taryn Reilly (Author) / Redding, Kevin (Thesis director) / Ghirlanda, Giovanna (Committee member) / Vermaas, Willem (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / School of Life Sciences (Contributor) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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Description
A novel underwater, open source, and configurable vehicle that mimics and leverages advances in quad-copter controls and dynamics, called the uDrone, was designed, built and tested. This vehicle was developed to aid coral reef researchers in collecting underwater spectroscopic data for the purpose of monitoring coral reef health. It is

A novel underwater, open source, and configurable vehicle that mimics and leverages advances in quad-copter controls and dynamics, called the uDrone, was designed, built and tested. This vehicle was developed to aid coral reef researchers in collecting underwater spectroscopic data for the purpose of monitoring coral reef health. It is designed with an on-board integrated sensor system to support both automated navigation in close proximity to reefs and environmental observation. Additionally, the vehicle can serve as a testbed for future research in the realm of programming for autonomous underwater navigation and data collection, given the open-source simulation and software environment in which it was developed. This thesis presents the motivation for and design components of the new vehicle, a model governing vehicle dynamics, and the results of two proof-of-concept simulation for automated control.
ContributorsGoldman, Alex (Author) / Das, Jnaneshwar (Thesis advisor) / Asner, Greg (Committee member) / Marvi, Hamidreza (Committee member) / Arizona State University (Publisher)
Created2020