Effect of glyphosate, its metabolite AMPA, and the glyphosate formulation Roundup ® on brown trout (Salmo trutta f. fario) gut microbiome diversity

Glyphosate is used worldwide as a compound of pesticides and is detectable in many environmental compartments. It enters water bodies primarily through drift from agricultural areas so that aquatic organisms are exposed to this chemical, especially after rain events. Glyphosate is advertised and sold as a highly specific herbicide, which interacts with the EPSP synthase, an enzyme of the shikimate metabolism, resulting in an inhibition of the synthesis of vital aromatic amino acids. However, not only plants but also bacteria can possess this enzyme, so that influences of glyphosate on microbiomes of exposed organisms cannot be excluded. Those influences may result in subtle and long-term effects, e.g. disturbance of the symbiotic interactions of bionts with microorganisms of their microbiomes.Mechanisms how glyphosate´s transformation product aminomethylphosphonic acid (AMPA) might interfere in this context is not understood so far. In the present study, molecular biological fingerprinting methods showed concentration-dependent effects of glyphosate and AMPA on fish microbiomes. In addition, age-dependent differences in the composition of the microbiomes regarding abundance and diversity were detected. ... mehrFurthermore, the effect of exposure to glyphosate and AMPA was investigated for several fish pathogens of gut microbiomes in terms of their gene expression of virulence factors associated with pathogenicity. In vitro transcriptome analysis with the fish pathogen Yersinia ruckeri revealed that it is at least questionable whether the observed effect on the microbiome is caused by the intended mode of action of glyphosate, namely the inhibition of EPSP synthase activity.