Reinaldo Alcalde of the University of Texas at Austin will present “Effects of S. oneidensis MR-1 Motility on Nitrate Biodegradation Along a Concentration Gradient of the Antibiotic Ciprofloxacin in a Diffusion-Controlled Microfluidic Gradient Chamber”.

Subsurface environments often contain contaminant mixtures, and
biodegradation of one pollutant may be inhibited by the toxicity of another. This is of particular interest in agricultural settings, where veterinary pharmaceuticals (e.g., antibiotics) can inhibit nitrate biodegradation. In this study, a microfluidic platform designed to generate diffusive solute gradients was fabricated to explore how antibiotic concentration gradients affect the ability of Shewanella
oneidenisis MR-1 to degrade nitrate. Our results show a surprising ecological response, where motility allows S. oneidensis MR-1 to migrate, persist and be metabolically active at high antibiotic concentrations (i.e. 50x MIC) when a flux of nutrient-rich compounds is present, despite the lack of antibiotic resistance
development. Control studies with limited nutrient fluxes and a non-motile ?fla mutant further confirm this response, and result in cell death and in minimal metabolic activity in the presence of high antibiotic concentrations, respectively. The results of this study differ from those in batch, and infer that chemotactic driven motility plays an important role in the microbial habitability and
degradation activity within toxic environments.