Herbicide use can increase the prevalence of antibiotic resistant bacteria in the soil, shows a New York University study, in the UK, published in the journal 'Molecular Biology and Evolution'.

Herbicides are one of the most widely used chemicals in agriculture, and while these compounds are used to attack weeds, can cause damage to soil microbes, such as bacteria and fungi, potentially changing the ecological properties of microbial communities.

Scientists from China and the UK studied the effect of three widely used herbicides called glyphosate, glufosinate, and dicamba on soil bacterial communities. Using soil microcosm, the researchers found that herbicides increased the relative abundance of bacterial species that carry antibiotic resistance genes.

This was because growth-enhancing mutations in the presence of herbicides also increased bacterial tolerance to antibiotics. Herbicide exposure also led to a more frequent movement of antibiotic resistance genes between bacteria.

Similar patterns were found in agricultural fields in 11 Chinese provinces, where history of herbicide application and levels of herbicide residues in the soil were associated with higher levels of antibiotic resistance genes.

El Dr. Ville Friman, from the Department of Biology, highlights that these results «suggest that herbicide use could indirectly drive the evolution of antibiotic resistance in agricultural soil microbiomes, which are repeatedly exposed to herbicides during weed control. '

“Interestingly, antibiotic resistance genes were favored at concentrations of herbicides that they were not lethal to bacteria -Add-. This shows that the already very low levels of herbicides could significantly change the genetic makeup of soil bacterial populations. '

At present, these effects are not taken into account by ecotoxicological risk assessments, which do not consider the evolutionary consequences of the prolonged application of chemical substances at the level of microbial communities, he warns.

'While antibiotic resistance genes are not harmful in themselves, reduce the effectiveness of antibiotics during clinical treatments He continues. Keeping the frequency of resistance genes low will prolong the long-term efficacy of antibiotics. As resistance genes can easily move between environments, agricultural fields could be an important global source of resistance genes.

The study concludes that the effects of these herbicide concentrations on microbial communities should be reassessed to fully understand the risks associated with the prevalence of antibiotic resistance genes.