Impact of antibiotic concentration gradients on nitrate reduction and antibiotic resistance in a microfluidic gradient chamber.

In order to explore the impact of antibiotics on the bacterial metabolic cycling of nitrate within contaminated soil and groundwater environments, we compared the effects of polymyxin B (PMB) and ciprofloxacin (CIP) concentration gradients on the distribution and activity of a wild type (WT) and a flagella deficient mutant (Δflag) of Shewanella oneidensis MR-1 in a microfluidic gradient chamber (MGC). Complementary batch experiments were performed to measure bacteriostatic versus bactericidal concentrations of the two antibiotics, as well as their effect on nitrate reduction. Prior work demonstrated that PMB disrupts cell membranes while CIP inhibits DNA synthesis.

The role of chemotaxis and efflux pumps on nitrate reduction in the toxic regions of a ciprofloxacin concentration gradient.

Spatial concentration gradients of antibiotics are prevalent in the natural environment. Yet, the microbial response in these heterogeneous systems remains poorly understood. We used a microfluidic reactor to create an artificial microscopic ecosystem that generates diffusive gradients of solutes across interconnected microenvironments.

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

A microfluidic gradient chamber (MGC) and a homogeneous batch culturing system were used to evaluate whether spatial concentration gradients of the antibiotic ciprofloxacin allow development of greater antibiotic resistance in strain 307 ( 307) compared to exclusively temporal concentration gradients, as indicated in an earlier study. A linear spatial gradient of ciprofloxacin and Luria-Bertani broth (LB) medium was established and maintained by diffusion over 5 days across a well array in the MGC, with relative concentrations along the gradient of 1.7-7.

Diffusion-Based Recycling of Flavins Allows Shewanella oneidensis MR-1 To Yield Energy from Metal Reduction Across Physical Separations.

We fabricated a microfluidic reactor with a nanoporous barrier to characterize electron transport between Shewanella oneidensis MR-1 and the metal oxide birnessite across a physical separation. Real-time quantification of electron flux across this barrier by strains with different electron transfer capabilities revealed that this bacterium exports flavins to its surroundings when faced with no direct physical access to an electron acceptor, allowing it to reduce metals at distances exceeding 60 μm. An energy balance indicates that flavins must be recycled for S.

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

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 Shewanella oneidenisis MR-1 to reduce the former in the presence of the latter.

Geobiology reveals how human kidney stones dissolve in vivo.

More than 10% of the global human population is now afflicted with kidney stones, which are commonly associated with other significant health problems including diabetes, hypertension and obesity. Nearly 70% of these stones are primarily composed of calcium oxalate, a mineral previously assumed to be effectively insoluble within the kidney. This has limited currently available treatment options to painful passage and/or invasive surgical procedures.