Motility of Shewanella oneidensis MR-1 Allows for Nitrate Reduction in the Toxic Region of a Ciprofloxacin Concentration Gradient in a Microfluidic Reactor

Abstract

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 diffusioncontrolled concentration gradients of nitrate and ciprofloxacin under anoxic conditions in order to evaluate the ability of Shewanella oneidenisis MR-1 to reduce the former in the presence of the latter. Results show a surprising ecological response, where swimming motility allow S. oneidensis 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 (Δf lag) 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.

Adaptive Evolution of Escherichia coli to Ciprofloxacin in Controlled Stress Environments: Contrasting Patterns of Resistance in Spatially Varying versus Uniformly Mixed Concentration Conditions

“…Since each MGC-extracted culture contained different subpopulations, we expected growth on plates of only those that adapted to at least the corresponding ciprofloxacin concentration. We note that in recent work, we measured the MIC of cells using several different methods (e.g., plating, liquid culture) with comparable results …”

In Vivo Entombment of Bacteria and Fungi during Calcium Oxalate, Brushite, and Struvite Urolithiasis

“…In these settings, cell wall surfaces, extracellular polymeric substances and other organic molecules produced and influenced by microbial metabolism can act as direct surface control on the rate and composition of crystalline mineral growth (6). In situ kinetic experiments in Yellowstone National Park carbonate hot springs have demonstrated that the physical cell presence and biomolecules produced by living microorganisms can more than double mineral precipitation rates compared to when they are absent (32). These direct catalytic influences (protein catalysis) (33) can now be linked to microbial gene targets identified by future microscopy-to-omics analyses in kidney stones.…”

Synergistic Effect of Co(III) and Co(II) in a 3D Structured Co3O4/Carbon Felt Electrode for Enhanced Electrochemical Nitrate Reduction Reaction

“…Compared to traditional physicochemical treatments, like physisorption, biological reduction, and ion exchange, − electrochemical reduction of nitrate has received more and more attention due to its characteristics such as simple operation, environment friendliness, and low cost. , The electrochemical nitrate reduction reaction (ENRR) is a complex reaction involving many intermediates . More importantly, the first step of electrochemically reducing nitrates to nitrites is the rate-determining step for the overall ENRR. , Thus, it is necessary to develop efficient cathodes for improving the rate of nitrate reduction.…”