Glyphosate is a widely used herbicide globally, applied to control weeds in agricultural and non-agricultural settings. It is the active ingredient in many commercial weed-killing products, including those sold under the brand name Roundup. While its primary function is to eliminate unwanted plants, a common question arises regarding whether glyphosate also acts as an antibiotic. This question stems from its known effects on certain biological pathways present in both plants and some microorganisms.
Understanding Glyphosate and Antibiotics
Glyphosate is a broad-spectrum systemic herbicide, which means it affects a wide range of plants and is absorbed by the foliage, then transported throughout the plant. In contrast, an antibiotic is a substance that inhibits the growth of or kills microorganisms, primarily bacteria. Antibiotics are specifically used in medicine to treat or prevent bacterial infections in humans and animals.
How Glyphosate Affects Plants
Glyphosate exerts its herbicidal effect by interfering with a specific metabolic pathway in plants called the shikimate pathway. This pathway is essential for plants to synthesize three aromatic amino acids: phenylalanine, tyrosine, and tryptophan. These amino acids are crucial for protein synthesis and overall plant growth. Glyphosate inhibits an enzyme within this pathway known as 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). By blocking the EPSPS enzyme, glyphosate prevents plants from producing these necessary amino acids, ultimately leading to their death.
The shikimate pathway is present in plants, fungi, and bacteria, but it is absent in animals, including humans. This absence in animals is often cited as a reason for glyphosate’s relatively low toxicity to them.
Glyphosate’s Effects on Bacteria
Glyphosate is not classified as a traditional antibiotic intended for treating bacterial infections in humans or animals. However, it can affect certain bacteria because, like plants, many bacteria also possess the shikimate pathway. This means that glyphosate can inhibit the EPSPS enzyme in these specific bacterial species, disrupting their ability to produce essential aromatic amino acids. Glyphosate’s antimicrobial activity has been described, and it has even been patented for its antibiotic properties against various bacteria, fungi, and parasites that contain the EPSPS enzyme. Therefore, while not a medical antibiotic, glyphosate can indeed have an incidental antibacterial effect on susceptible microorganisms.
Implications for the Microbiome
The ability of glyphosate to affect bacteria that possess the shikimate pathway has implications for complex microbial communities, such as the gut microbiome in humans and animals. By inhibiting certain bacterial species that rely on this pathway, glyphosate has the potential to alter the balance and composition of microbial populations within the gut. Studies have indicated that more than half of bacterial species in the core human gut microbiome could be sensitive to glyphosate. This selective inhibition could lead to shifts in the gut microbiota, potentially favoring glyphosate-resistant bacteria while reducing the abundance of sensitive, often beneficial, species. While research is ongoing, these changes in microbial balance highlight the potential for glyphosate to influence the overall dynamics of the microbiome.