Characterizing the soil microbiome and quantifying antibiotic resistance gene dynamics in agricultural soil following swine CAFO manure application

PLoS One. 2019 Aug 19;14(8):e0220770. doi: 10.1371/journal.pone.0220770. eCollection 2019.

Abstract

As agriculture industrializes, concentrated animal feeding operations (CAFOs) are becoming more common. Feces from CAFOs is often used as fertilizer on fields. However, little is known about the effects manure has on the soil microbiome, which is an important aspect of soil health and fertility. In addition, due to the subtherapeutic levels of antibiotics necessary to keep the animals healthy, CAFO manure has elevated levels of antibiotic resistant bacteria. Using 16s rRNA high-throughput sequencing and qPCR, this study sought to determine the impact of swine CAFO manure application on both the soil microbiome and abundance of select antibiotic resistance genes (ARGs) and mobile element genes (erm(B), erm(C), sul1, str(B), intI1, IncW repA) in agricultural soil over the fall and spring seasons. We found the manure community to be distinct from the soil community, with a majority of bacteria belonging to Bacteroidetes and Firmicutes. The soil samples had more diverse communities dominated by Acidobacteria, Actinobacteria, Proteobacteria, Verrucomicrobia, and unclassified bacteria. We observed significant differences in the soil microbiome between all time points, except between the spring samples. However, by tracking manure associated taxa, we found the addition of the manure microbiome to be a minor driver of the shift. Of the measured genes, manure application only significantly increased the abundance of erm(B) and erm(C) which remained elevated in the spring. These results suggest bacteria in the manure do not survive well in soil and that ARG dynamics in soil following manure application vary by resistance gene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agriculture
  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Bacteria / drug effects
  • Bacteria / genetics
  • Bacteria / isolation & purification*
  • Drug Resistance, Microbial
  • Genes, Bacterial
  • Manure / microbiology*
  • Soil Microbiology*
  • Swine / microbiology

Substances

  • Anti-Bacterial Agents
  • Manure

Grants and funding

This work was funded by the Leopold Center for Sustainable Agriculture (E2016-08) SHL, USDA-NIFA-AFRI (2015-07849) SHL and AH, and Grinnell College SHL, EL, AC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The funders URLs are: https://www.leopold.iastate.edu/leopold-center-sustainable-agriculture; https://nifa.usda.gov/program/agriculture-and-food-research-initiative-afri; https://www.grinnell.edu/.