ORIGINAL ABSTRACT

Despite extensive research into the toxicology of the herbicide glyphosate, there are still major unknowns regarding its effects on the human gut microbiome. We describe the effects of glyphosate and a Roundup glyphosate-based herbicide on infant gut microbiota using SHIME technology. SHIME microbiota culture was undertaken in the presence of a concentration of 100-mg/L glyphosate and the same glyphosate equivalent concentration of Roundup. Roundup and to a lesser extent glyphosate caused an increase in fermentation activity, resulting in acidification of the microbial environment. This was also reflected by an increase in lactate and acetate production concomitant to a decrease in the levels of propionate, valerate, caproate and butyrate. Ammonium production reflecting proteolytic activities was increased by Roundup exposure. Global metabolomics revealed large-scale disturbances, including an increased abundance of long-chain polyunsaturated fatty acids. Changes in bacterial composition measured by qPCR and 16S rRNA suggested that lactobacilli had their growth stimulated as a result of microenvironment acidification. Co-treatment with the spore-based probiotic formulation MegaSporeBiotic reverted some of the changes in short-chain fatty acid levels. Altogether, our results suggest that glyphosate can exert effects on human gut microbiota.