ORCID
https://orcid.org/0000-0003-4618-9155
Date of Award
12-18-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Microbial metabolisms are incredibly versatile and dynamic, allowing adaptive strategies for growth in even the most limiting environments. For an ever-increasing number of microbes, this includes utilizing soluble or insoluble inorganic mineral species as electron donors, driving geochemical cycles and microbial metabolisms. This metabolic function of transporting electrons derived from the extracellular environment across cell membranes is called extracellular electron uptake (EEU). Within (photo)autotrophs, (p)EEU also sustains CO2 fixation to cell biomass, implicating a potentially fundamental role of microbial carbon cycling in aquatic and soil ecosystems. A model metabolic scheme of pEEU occurring in natural environments is photoferrotrophy, which pairs oxidation of iron minerals to CO2 fixation. In laboratory settings, pEEU can occur under poised electrodes as electron donors in bioelectrochemical systems. In the last decade, photoferrotrophy has been extensively studied in a model photoferrotrophy Rhodopseudomonas palustris TIE-1, identifying a three-gene operon (pio) required for pEEU. While this system has been imperative to understanding pEEU at the molecular level in TIE-1, the Pio system is not conserved within all pEEU-capable organisms. We sought to characterize pEEU transfer mechanisms in a collection of marine purple non-sulfur bacteria isolated from a microbial mat. This initial work produced nearly 30 isolates, 15 of which were identified as Rhodovulum sulfidophilum. A representative strain, AB26, was then individually chosen for characterization of photoferrotrophy and pEEU, and a novel pEEU uptake di-heme c-type cytochrome EeuP was identified. The objective of the work within this dissertation was to further expand pEEU in these novel isolates, as none of them contained known homologs of pEEU mechanisms. In Chapter 2, I show that due to an increase in genome sequencing data, two of our isolates, including AB26, are taxonomically re-identified as R. visakhapatnamense. I then described the AB26 genome, as outside of these two isolates, a single R. visakhapatnamense genome is publicly available. Using transcriptomes of AB26 from pEEU, I also compared genomic contents of all 15 Rhodovulum spp. genomes for conserved or unique pEEU-potential genes. In Chapter 3, I show another novel strain R. sulfidophilum AB33 is capable of photoferrotrophy and pEEU. Using proteomics under photoferrotrophy and pEEU as compared to photoautotrophy, I describe key cellular processes under these conditions. I constructed two deletion mutants in AB33: an EeuP homolog and a novel mono-heme c-type cytochrome AceA. Using bioelectrochemical systems I show both proteins are implicated for current uptake from an electrode. This work shows pEEU is likely common in diverse environments and does not rely on all genes required for this process to be organized in operons. Further, AB33 responds differently to pEEU and photoferrotrophy. What remains to be understood in these microbes includes remaining electron transfer proteins involved in either metabolism, how AB33 (and Rhodovulum spp. at large) sense different electron donors, and regulation of uptake systems.
Language
English (en)
Chair and Committee
Sebla Kutluay
Committee Members
Arpita Bose; Barbara Kunkel; George Bullerjahn; Joshua Van Dyke-Blodgett; Mikhail Tikhonov
Recommended Citation
Davenport, Emily J., "Multi-omic analysis of phototrophic extracellular electron uptake in novel Rhodovulum spp. isolated from a marine estuary" (2024). Arts & Sciences Electronic Theses and Dissertations. 3367.
https://openscholarship.wustl.edu/art_sci_etds/3367