Prairie strips remove swine manure associated antimicrobial resistance genes and bacteria from runoff

Runoff from manured agricultural fields can transport antimicrobial resistance (AMR) contaminants, including genes and bacteria, to downstream ecosystems. Previous work has identified the integration of Conservation Practice 43 (CP 43) prairie strips – a type of vegetative filter strip – within and at the edge of agricultural fields as a potential management solution to reduce the movement of these, and other, manure pollutants, while offering an opportunity for biodiversity conservation. The objectives of this study were to 1) quantify the ability of prairie strips to reduce the presence of antimicrobial resistance genes from manure laden runoff, and 2) characterize the impact of manure on prairie soil microbiomes over time. Simulated rainfall events were used to create artificial runoff on field plots with swine manure amendment and prairie strips as treatment factors. A suite of antibiotic resistance genes and mobile genetic elements were characterized in runoff samples collected during the rainfall simulation, while manure associated bacteria were characterized in soil samples collected over 153 days after the rainfall simulation. Prairie strips placed downslope from manured crop soil significantly reduced the cumulative abundance of resistance genes in both runoff water (p-value < 0.0001) and runoff sediment (p-value < 0.0001). Manure associated bacteria were transported both horizontally, from the manure amended crop soil into the prairie strip soil, and vertically, into the crop and prairie strip soil profiles. The specific manure associated gene tet(M) and the specific manure associated bacterial genus Clostridium sensu stricto 1 were highly enriched in manured runoff and soil, respectively, and could represent future targets of human health concern. Results from this study provide further support for the use of CP 43 prairie strips as a management practice to reduce the transport of manure associated resistance contaminants off agricultural fields.This article is published as Alt, Laura M., Jared S. Flater, Adina Howe, Thomas B. Moorman, Lisa A. Schulte, and Michelle L. Soupir. "Prairie strips remove swine manure associated antimicrobial resistance genes and bacteria from runoff." Agriculture, Ecosystems & Environment 349 (2023): 108469. DOI: 10.1016/j.agee.2023.108469. Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted

Prairie strips’ effect on transport of antimicrobial resistance indicators in poultry litter

Poultry litter is a valuable nutrient resource for agricultural production but is also a potential source for introducing antibiotic resistance genes (ARGs) and litter-associated bacteria (LAB) to the environment. Prairie strips have been demonstrated as an effective conservation practice to improve environmental quality in agroecosystems. This research aims to assess prairie strips’ potential for reducing the transport of LAB and ARGs in runoff after litter application. Plot-scale rainfall simulations were performed using a replicated block design, with soil and surface runoff samples taken during the rainfall event. Microbial taxa and ARGs were characterized in the litter, soil, and water samples. In plots with litter application, LAB and ARGs were mainly detected in runoff, with very low detection in soils. Detection of ARGs in runoff, irrespective of strip installations, is consistent with previous observations of litter as a source of antimicrobial resistance (AMR) risks. The effectiveness of prairie strips to remove LAB and ARGs varied. In two of the three prairie strip plots, fewer AMR indicators were detected relative to control plots, suggesting that the prairie strips can potentially reduce these risks. In one plot, which was also associated with increased flow rate, we observed increased AMR indicators despite the installation of a prairie strip. Our observations highlight the need to prioritize understanding of soil properties even within the same site. Although we show that prairie strips can potentially reduce AMR risks, further research is needed to better understand the influence of rainfall timing, soil, and litter characteristics.This is the published version of the following article: Flater, Jared S., Laura M. Alt, Michelle Soupir, Thomas B. Moorman, and Adina Howe. Prairie Strips Impact on Transport of Antimicrobial Resistance Indicators in Poultry Litter. 2022. DOI: 10.1002/jeq2.20333. Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted

Relationship Between Molecular Contact Thermodynamics and Surface Contact Mechanics

Measurements have been made of the adhesion and friction forces between organic monolayers in heptane/ acetone mixtures using an atomic force microscope (AFM). It has been found that the contact mechanics are best modeled by treating the friction force as the sum of a load-dependent term (attributed to “molecular plowing”) and an areadependent term attributed to shearing (adhesion). The relative contributions of plowing and shearing are determined by the coefficient of friction, μ, and the surface shear strength τ. The transition from adhesion- to load-determined friction is controlled by the solvation state of the surface: solvated surfaces represent a limiting case in which the shear term approaches zero, and the friction-load relationship is linear, while in other circumstances, the friction-load relationship is nonlinear and consistent with Derjaguin−Muller−Toporov mechanics. A striking correlation has been observed between the concentration-dependence of the association constant (Ka) for the formation of 1:1 hydrogen-bonded complexes and the pull-off force Fa and surface shear strength τ for the same molecules when one partner is immobilized by attachment to an AFM probe and the other is adsorbed to a surface. Analysis of the concentration-dependence of Fa and τ enables the prediction of KS with remarkably high precision, indicating that for these hydrogen bonding systems, the tip−sample adhesion is dominated by the H-bond thermodynamics. For mixed monolayers, H-bond thermodynamics dominate the interaction even at very low concentrations of the H-bond acceptor. Even for weakly adhering systems, a nonlinear frictionload relationship results. The variation in τ with the film composition is correlated very closely with the variation in Fa. However, the coefficient of friction varies little with the film composition and is invariant with the strength of tip−sample adhesion, being dominated by molecular plowing and, for sufficiently large concentrations of hydroxyl terminated adsorbates, the disruption of intramonolayer hydrogen bonding interactions