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- Genre: Masters Thesis
Description
Sinking particles are important conduits of organic carbon from the euphotic zone to the deep ocean and microhabitats for diverse microbial communities, but little is known about what determines their origin and community composition. Events in the northwestern Sargasso Sea, such as winter convective mixing, summer stratification, and mesoscale (10–100 km) eddies, characteristic features of this region, affect the vertical and temporal composition and abundance of pelagic and particle-attached microorganisms. To assess the connections of the microbial communities between the euphotic zone and sinking particles, I carried out indicator and differential abundance analyses of prokaryotes and photoautotrophs based on the V4-V5 amplicons of the 16S rDNA from samples collected in the Sargasso Sea during the spring and summer of 2012. I found that gammaproteobacteria such as Pseudoalteromonas sp. and Vibrio sp., common particle-associated bacteria often linked with zooplankton, dominated the sequence libraries of the sinking particles. The analysis also revealed that members of Flavobacteria, particularly the fish pathogen Tenacibaculum sp., as well as Chloropicon sp. and Chloroparvula sp., among the smallest known green algae, were indicators taxa of sinking particles. The cryptophyte Teleaulax and the diatom Chaetoceros were overrepresented in the particle communities during both seasons. Interestingly, I also found that the large centric diatom, Rhizosolenia sp., generally rare in the oligotrophic Sargasso Sea, dominated photoautotrophic communities of sinking particles collected in the center of an anticyclonic eddy with unusual upwelling due to eddy-wind interactions. I hypothesize that the steady contribution by picophytoplankton to particle flux is punctuated by pulses of production and flux of larger-sized phytoplankton in response to episodic eddy upwelling events and can lead to higher export of particulate organic matter during the summer.
ContributorsFontánez Ortiz, Marc Alec (Author) / Neuer, Susanne (Thesis advisor) / Zhu, Qiyun (Committee member) / Trembath-Reichert, Elizabeth (Committee member) / Arizona State University (Publisher)
Created2022
Description
All known life requires three main metabolic components to grow: an energy source, an electron source, and a carbon source. For energy, an organism can use light or chemical reactions. For electrons, an organism can use metals or organic molecules. For carbon, an organism can use organic or inorganic carbon. Life has adapted to use any mixture of the endpoints for each of the three metabolic components. Understanding how these components are incorporated in a living bacterium on Earth in modern times is relatively straight forward. This becomes much more complicated when trying to determine what metabolisms may have been used in ancient times on Earth or potential novel metabolisms that exist on other planets. One way to examine these possibilities is by creating genetically modified mutant bacteria that have novel metabolisms or proposed ancient metabolisms to study. This thesis is the beginning of a broader study to understand novel metabolisms using Heliobacteria modesticaldum. H. modesticaldum was grown under different environmental conditions to isolate the impacts of energy, electron, and carbon sources on carbon and nitrogen isotope fractionation. Additionally, the wild type and a novel mutant H. modesticaldum were compared to measure the effects of specific enzymes on carbon and nitrogen isotope fractionation. By forcing the bacterium to adapt to different conditions, variation in carbon and nitrogen content and isotopic signature are detected. Specifically, by forcing the bacterium to fix nitrogen as opposed to nitrogen incorporation, the isotopic signature of the bacterium had a noticeable change. Themutant H. modesticaldum also had a different isotopic signature than the wild type. Without the enzyme citrate synthase, H. modesticaldum had to adapt its carbon metabolic cycle, creating a measurable carbon isotope fractionation. The results described here offer new insight into the effects of metabolism on carbon and nitrogen fractionation of ancient or novel organisms.
ContributorsElms, Nicholas (Author) / Hartnett, Hilairy E (Thesis advisor) / Redding, Kevin (Committee member) / Trembath-Reichert, Elizabeth (Committee member) / Anbar, Ariel D (Committee member) / Arizona State University (Publisher)
Created2021
Description
Drylands make up more than 45% of the Earth’s land surface and are essential to agriculture and understanding global carbon and elemental cycling. This thesis presents an analysis of atmospheric relative humidity (RH) and temperature (T) as they impact soil moisture and water content at two dryland sites. In particular, this thesis assesses the likelihood and impact of non-rainfall moisture (NRM) sources on dryland soils. This work also includes a discussion of the development and testing of a novel environmental sensing network, using custom nodes called EarthPods, and recommendations for the collection of future data from dryland sites to better understand NRM events in these regions. An analysis of weather conditions at two drylands sites suggest that nighttime RH is frequently high enough for NRM events to occur. Thesis results were unable to detect changes in soil water content based on historical weather data, likely due to instrument limitations (depth and sensitivity of soil moisture probes) and the small changes in soil moisture during NRM events. However, laboratory tests of EarthPod soil moisture sensors indicated strong sensitivity to T. Characterization of these T sensitivities provide opportunities to calibrate and correct soil moisture estimates using these sensors in the future. This work provides the foundation for larger biogeochemical sampling campaigns focusing on NRM in dryland systems.
ContributorsHanan, Desmond (Author) / Trembath-Reichert, Elizabeth (Thesis advisor) / Das, Jnaneshwar (Committee member) / Throop, Heather (Committee member) / Arizona State University (Publisher)
Created2021
Description
Universal biology is an important astrobiological concept, specifically for the search for life beyond Earth. Over 1.2 million species have been identified on Earth, yet all life partakes in certain processes, such as homeostasis and replication. Furthermore, several aspects of biochemistry on Earth are thought to be universal, such as the use of organic macromolecules like proteins and nucleic acids. The presence of many biochemical features in empirical data, however, has never been thoroughly investigated. Moreover, the ability to generalize universal features of Earth biology to other worlds suffers from the epistemic problem of induction. Systems biology approaches offer means to quantify abstract patterns in living systems which can more readily be extended beyond Earth’s familiar planetary context. In particular, scaling laws, which characterize how a system responds to changes in size, have met with prior success in investigating universal biology.
This thesis rigorously tests the hypothesis that biochemistry is universal across life on Earth. The study collects enzyme data for annotated archaeal, bacterial, and eukaryotic genomes, in addition to metagenomes. This approach allows one to quantitatively define a biochemical system and sample across known biochemical diversity, while simultaneously exploring enzyme class scaling at both the level of both individual organisms and ecosystems. Using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the Joint Genome Institute’s Integrated Microbial Genomes and Microbiomes (JGI IMG/M) database, this thesis performs the largest comparative analysis of microbial enzyme content and biochemistry to date. In doing so, this thesis quantitatively explores the distribution of enzyme classes on Earth and adds constraints to notions of universal biochemistry on Earth.
This thesis rigorously tests the hypothesis that biochemistry is universal across life on Earth. The study collects enzyme data for annotated archaeal, bacterial, and eukaryotic genomes, in addition to metagenomes. This approach allows one to quantitatively define a biochemical system and sample across known biochemical diversity, while simultaneously exploring enzyme class scaling at both the level of both individual organisms and ecosystems. Using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the Joint Genome Institute’s Integrated Microbial Genomes and Microbiomes (JGI IMG/M) database, this thesis performs the largest comparative analysis of microbial enzyme content and biochemistry to date. In doing so, this thesis quantitatively explores the distribution of enzyme classes on Earth and adds constraints to notions of universal biochemistry on Earth.
ContributorsGagler, Dylan (Author) / Walker, Sara I (Thesis advisor) / Kempes, Chris (Committee member) / Trembath-Reichert, Elizabeth (Committee member) / Arizona State University (Publisher)
Created2020
Description
Methanogens anaerobically metabolize simple carbon compounds coupled with an electron donor and produce methane in a process known as methanogenesis. While their importance in anoxic ecosystems and their greenhouse gas emissions are known, less is known about their diverse members. This is in part due to limited culture-dependent studies as a consequence of the difficulty to culture and isolate them under laboratory conditions. Current methods in methanogen isolation require lengthy protocols, expensive equipment, can be easily contaminated, and even if a successful isolation is completed, traditional methods are biased towards only a few species of methanogens- leaving much of this community unsampled and thus unrepresented. New approaches in the isolation of methanogens need to be investigated in order to circumvent these obstacles. Here, I evaluated the effects of different strategies and alternative methods with the goal of increasing the diversity of recovered methanogens from Amazon peatlands as a study case. The results show that: a) through the use of different antibiotics the bacterial community makeup can be altered and lead to different methanogenic enrichments, some antibiotics reliably increase methanogenesis in all study sites, others only enhance it in some sites, while some have a low rate of methanogenesis enriching novel slow growers, b) the use of different substrates has less of an effect on methane production rates, however the complex substrate butyrate leads to consistent late stimulation, c) altering media components (reducing agent and overall geochemical background) for Amazon conditions would lead to a shorter time to isolation, d) and multiple methanogenic enrichments were achieved building on variable conditions and can lead to novel Amazon lineages. Molecular data is offering a more detailed view of bacteria and methanogens increasing or decreasing in response to treatments. Overall, it is shown that combining alternative approaches that manipulate interactions, metabolic substrate availability and culturing conditions could lead to more diverse isolation outputs from methanogenic cultures.
ContributorsAyers, Jillian (Author) / Cadillo-Quiroz, Hinsby (Thesis advisor) / Shi, Yixin (Committee member) / Trembath-Reichert, Elizabeth (Committee member) / Arizona State University (Publisher)
Created2021