Emerging Bacterial Resistance and Genotoxicity of Water-Soluble Fractions of Agricultural Soils from the Semiarid Region of Brazil Affected by the Continuous Use of Glyphosate

Abstract

The use of herbicides in modern agriculture has been the subject of ongoing debate due to their negative impacts on the environment and human health. The aim of this study was to assess the bacterial, physicochemical and genotoxicity parameters of three soil samples of public farming settlements in Petrolândia, Brazil. The bacterial resistance patterns were examined after soil exposures to a known concentration of glyphosate (2.5%). Genotoxicity was assessed through the Drosophila melanogaster Comet assay, exposed to water-soluble fraction (WSF) soil samples, followed by the quantification of seven chemical elements. The results indicated that, although physicochemical parameters remained within acceptable limits, there was a significant presence of resistant bacteria, particularly Stenotrophomonas maltophilia, Bacillus cereus and Enterobacter cloacae. Comet assay results (Damage Index and Damage Frequency) presented a significant level of genotoxicity in two of the three WSFs. Clustering analysis associated the genetic damage to the presence of chrome and zinc heavy metals. The predominance of multidrug-resistant bacteria, combined with levels of genotoxicity, suggests that these soils exposed to glyphosate contamination represents a risk to the sustainability of Brazilian semiarid agriculture.