Expanding the Understanding of Extracellular Electron Transfer Mechanisms and the Physiological Impacts in Gram-Positive Bacteria

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dc.contributor.advisorAjo-Franklin, Caroline Men_US
dc.creatorTolar, Joe Gen_US
dc.date.accessioned2023-01-03T22:45:20Zen_US
dc.date.created2022-12en_US
dc.date.issued2022-11-30en_US
dc.date.submittedDecember 2022en_US
dc.date.updated2023-01-03T22:45:20Zen_US
dc.description.abstractLactic acid bacteria are named for their nearly exclusive fermentative metabolism. Thus, the recent observation of extracellular electron transfer (EET) activity - typically associated with anaerobic respiration in Gram-negative bacteria - in this class of organisms has forced researchers to rethink the rules governing microbial metabolic strategies (Tejedor-Sanz et al., 2022). Lactic acid bacteria also differ from model EET microorganisms in their cell envelope structure and the niches they inhabit. These differences open important questions: What mechanisms do lactic acid bacteria use to accomplish EET? What are the physiological effects of EET on lactic acid bacteria? Here I address these questions by exploring the role of quinones and flavins in EET by Lactiplantibacillus plantarum (Chapter 2), by developing methods to monitor gene expression in L. plantarum under EET conditions (Chapter 3), and by characterizing the physiological implications of EET in Enterococcus faecalis (Chapter 4). I discovered that either the quinone, 1,4-dihydroxy-2-naphthoic acid (DHNA), or riboflavin support EET via similar, but unique pathways. Using genetic knockouts of candidate genes and electrochemical techniques, I constructed a working model of the EET mechanism for DHNA and riboflavin. Next, I developed a methodology to screen and validate fluorescent reporters of promoter activity under EET conditions to provide insight into the mechanism of the EET-induced fermentative metabolism changes. Additionally, I found that growth conditions and carbon sources can dramatically influence EET activity in E. faecalis. Lastly, I developed a method to quantify interspecies competition between E. faecalis and Staphylococcus aureus and simultaneously measure EET activity. Understanding the role of EET in lactic acid bacteria is of great importance due to the significance of lactic acid bacteria in agriculture, bioremediation, food production, and gut health. This work expands our molecular-level understanding of EET in Gram-positive microbes and provides additional opportunities to manipulate EET for biotechnology.en_US
dc.embargo.lift2024-12-01en_US
dc.embargo.terms2024-12-01en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.citationTolar, Joe G. "Expanding the Understanding of Extracellular Electron Transfer Mechanisms and the Physiological Impacts in Gram-Positive Bacteria." (2022) Diss., Rice University. <a href="https://hdl.handle.net/1911/114197">https://hdl.handle.net/1911/114197</a>.en_US
dc.identifier.urihttps://hdl.handle.net/1911/114197en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectlactic acid bacteriaen_US
dc.subjectquinonesen_US
dc.subjectflavinsen_US
dc.subjectextracellular electron transfer mechanismen_US
dc.subjectmetabolismen_US
dc.subjectmicrobiologyen_US
dc.titleExpanding the Understanding of Extracellular Electron Transfer Mechanisms and the Physiological Impacts in Gram-Positive Bacteriaen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentBiochemistry and Cell Biologyen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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