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Motility of <i>Shewanella oneidensis</i> MR‑1 Allows for Nitrate Reduction in the Toxic Region of a Ciprofloxacin Concentration Gradient in a Microfluidic Reactor

By Reinaldo E. Alcalde (6333908), Kyle Michelson (1625059), Lang Zhou (1925722), Emily V. Schmitz (6333911), Jinzi Deng (1952518), Robert A. Sanford (272160), Bruce W. Fouke (251558) and Charles J. Werth (1277373)


Subsurface environments often contain mixtures of contaminants in which the microbial degradation of one pollutant may be inhibited by the toxicity of another. Agricultural settings exemplify these complex environments, where antimicrobial leachates may inhibit nitrate bioreduction, and are the motivation to address this fundamental ecological response. In this study, a microfluidic reactor was fabricated to create diffusion-controlled concentration gradients of nitrate and ciprofloxacin under anoxic conditions in order to evaluate the ability of <i>Shewanella oneidenisis</i> MR-1 to reduce the former in the presence of the latter. Results show a surprising ecological response, where swimming motility allow <i>S. oneidensis</i> MR-1 to accumulate and maintain metabolic activity for nitrate reduction in regions with toxic ciprofloxacin concentrations (i.e., 50× minimum inhibitory concentration, MIC), despite the lack of observed antibiotic resistance. Controls with limited nutrient flux and a nonmotile mutant (Δ<i>flag)</i> show that cells cannot colonize antibiotic rich microenvironments, and this results in minimal metabolic activity for nitrate reduction. These results demonstrate that under anoxic, nitrate-reducing conditions, motility can control microbial habitability and metabolic activity in spatially heterogeneous toxic environments

Topics: Biochemistry, Microbiology, Cell Biology, Ecology, Virology, Space Science, Environmental Sciences not elsewhere classified, Biological Sciences not elsewhere classified, Chemical Sciences not elsewhere classified, MIC, nitrate reduction, Shewanella oneidenisis MR, antibiotic, Ciprofloxacin Concentration Gradient, diffusion-controlled concentration gradients, anoxic, oneidensi, ciprofloxacin, motility, Microfluidic Reactor Subsurface environments, response
Year: 2019
DOI identifier: 10.1021/acs.est.8b04838.s001
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Provided by: FigShare
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