Document Type
Article
Publication Date
4-25-2025
Publisher
American Society for Microbiology
Source Publication
Applied and Environmental Microbiology
Source ISSN
0099-2240
Original Item ID
DOI: 10.1128/aem.02222-24
Abstract
In many aquatic and terrestrial ecosystems, iron (Fe) reduction by microorganisms is a key part of biogeochemical cycling and energy flux. The presence of redox-active electron shuttles in the environment potentially enables a phylogenetically diverse group of microbes to use insoluble iron as a terminal electron acceptor. We investigated the impact that different electron shuttles had on respiration, microbial physiology, and microbial ecology. We tested eight different electron shuttles, seven quinones and riboflavin, with redox potentials between 0.217 and −0.340 V. Fe(III) reduction coupled with acetate oxidation was observed with all shuttles. Once Fe(III) reduction began to plateau, a rapid increase in acetate consumption was observed and coincided with the onset of methane production, except in the incubations with the shuttle 9,10-anthraquinone-2-carboxylic acid (AQC). The rates of iron reduction, acetate consumption, methanogenesis, and the microbial communities varied significantly across the different shuttles independent of redox potential. In general, shuttles appeared to reduce the overall diversity of the community compared to no shuttle controls, but certain shuttles were exceptions to this trend. Geobacteraceae were the predominant taxonomic family in all enrichments except in the presence of AQC or 1,2-dihydroxyanthraquinone (AQZ), but each shuttle enriched a unique community significantly different from the no shuttle control conditions. This suggests that the presence of different redox-active electron shuttles can have a large influence on the microbial ecology and total carbon flux in the environment.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Thapa, Bhim Sen; Flynn, Theodore M.; Jensvold, Zena D.; Kemner, Kenneth M.; Sladek, Margaret F.; O'Loughlin, Edward J.; and Marshall, Christopher W., "Effects of Soluble Electron Shuttles on Microbial Iron Reduction and Methanogenesis" (2025). Biological Sciences Faculty Research and Publications. 978.
https://epublications.marquette.edu/bio_fac/978
Comments
Published version. Applied and Environmental Microbiology, Vol. 91, No. 5 (April 25, 2025). DOI. © Thapa et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.