Glyphosate induces the synthesis of ppGpp

Area of Science:

• Microbiology
• Biochemistry
• Toxicology

Background:

• Glyphosate is a widely used herbicide inhibiting EPSP synthase, crucial for aromatic amino acid biosynthesis in plants and bacteria.
• The stringent response is a bacterial adaptation to stress, often triggered by amino acid starvation.

Purpose of the Study:

• To investigate the effect of glyphosate on bacterial physiology, specifically in Escherichia coli.
• To determine if glyphosate induces the stringent response and its underlying mechanisms.

Main Methods:

• Treating E. coli with glyphosate and observing growth.
• Measuring the accumulation of guanosine polyphosphates (ppGpp and pppGpp).
• Utilizing mutant strains (RelA, GppA) to elucidate the role of specific enzymes.

Main Results:

• Glyphosate treatment caused E. coli growth arrest and accumulation of ppGpp.
• These effects were reversed by adding aromatic amino acids.
• ppGpp accumulation was dependent on RelA, but pppGpp was not detected in wild-type strains.
• In a gppA mutant, both ppGpp and pppGpp accumulated upon glyphosate exposure.

Conclusions:

• Glyphosate induces a reversible stringent response in E. coli, characterized by amino acid starvation.
• The findings highlight a novel mechanism of glyphosate toxicity in bacteria.
• The stringent response pathway, involving RelA, plays a key role in the bacterial response to glyphosate.