February 24, 2021 | Soil sprayed with weed killers glyphosate, glufosinate, or dicamba are likely to contain higher amounts of antibiotic resistant bacteria, according to research published in Molecular Biology and Evolution. Each year in the U.S., at least two million people develop an antibiotic resistant infection and over 23,000 die. Authors of the study say widespread herbicide use is likely playing a role. “Our results suggest that the use of herbicides could indirectly drive antibiotic resistance evolution in agricultural soil microbiomes, which are repeatedly exposed to herbicides during weed control,” said Ville Friman, PhD of the University of York in the United Kingdom. Scientists began their investigation by looking at changes to soil communities in soil microcosms over the course of roughly two months. Microcosms were grouped by the herbicide applied, while a control microcosm remained unexposed. Contrary to the pesticide industry’s claim that these chemicals break down quickly and become inert by binding to soil particles, large proportions of the herbicides remain in the soil at the end of the 60-day experiment, stemming back from the first application. For glyphosate, 18% remained, glufosinate 21%, and dicamba 34%. Although no significant changes to bacterial diversity, abundance, or richness were observed, researchers found that herbicide-exposed soils contain a greater abundance of genes associated with antibiotic resistance, as well as a higher number of mobile genetic elements. [Liao, Han- peng et al. Herbicide Selection Promotes Antibiotic Resistance in Soil Microbiomes. Molecular Biology and Evolution. 38(6):2337–2350. 2021.]
