Quantification of the Potential Impact of Glyphosate-Based Products on Microbiomes

Abstract

Glyphosate-based products (GBP) are the most common broad-spectrum herbicides worldwide. The target of glyphosate is the enzyme 5-enolpyruvylshikimate-3phosphate synthase (EPSPS) in the shikimate pathway, which is virtually universal in plants. The inhibition of the enzyme stops the production of three essential amino acids: phenylalanine, tyrosine, and tryptophan. EPSPS is also present in fungi and prokaryotes, such as archaea and bacteria; thus, the use of GBP may have an impact on the microbiome composition of soils, plants, herbivores, and secondary consumers. This article aims to present general guidelines to assess the effect of GBP on microbiomes from field experiments to bioinformatics analyses and provide a few testable hypotheses. Two field experiments are presented to test the GBP on non-target organisms. First, plant-associated microbes from 10 replicated control and GBP treatment plots simulating no-till cropping are sampled and analyzed. In the second experiment, samples from experimental plots fertilized by either poultry manure containing glyphosate residues or non-treated control manure were obtained.Bioinformatics analysis of EPSPS protein sequences is utilized to determine the potential sensitivity of microbes to glyphosate. The first step in estimating the effect of GBP on microbiomes is to determine their potential sensitivity to the target enzyme (EPSPS). Microbial sequences can be obtained either from public repositories or by means of PCR amplification. However, in the majority of field studies, microbiome composition has been determined based on universal DNA markers such as the 16S rRNA and the internal transcribed spacer (ITS). In these cases, sensitivity to glyphosate can only be estimated through a probabilistic analysis of EPSPS sequences using closely related species. The quantification of the potential sensitivity of organisms to glyphosate, based on the EPSPS enzyme, provides a robust approach for further experiments to study target and non-target resistant mechanisms.

Crop and pesticide effects on gut microbiota and neurological functions: a review

“…Glyphosate is the most widely used herbicide worldwide due to its effectiveness and low toxicity [128]. It inhibits 5-enolpyruvylshikimic acid-3-phosphate synthase (EPSPS), which is essential for the biosynthesis of the amino acids phenylalanine, tyrosine, and tryptophan through the shikimic acid pathway [128,129]. Notably, this pathway is plant-specific and is considered safe for humans; however, it is also found in plants, bacteria, fungi, and prokaryotes, consequently affecting soil and human gut bacteria [129,130].…”

“…It inhibits 5-enolpyruvylshikimic acid-3-phosphate synthase (EPSPS), which is essential for the biosynthesis of the amino acids phenylalanine, tyrosine, and tryptophan through the shikimic acid pathway [128,129]. Notably, this pathway is plant-specific and is considered safe for humans; however, it is also found in plants, bacteria, fungi, and prokaryotes, consequently affecting soil and human gut bacteria [129,130]. Glyphosate action is non-selective in plants, although its effects vary among bacterial species [131].…”