Glyphosate in Roundup Affects Siderophore Synthesis in Pseudomonas fluorescens
Faculty Mentor Information
Dr. Hartzell and Dr. Ederer
Abstract
Glyphosate is the most widely used broad spectrum herbicide worldwide. Glyphosate use has increased over 15–fold since the introduction of glyphosate resistant (Roundup Ready) crops in 1996. Given this significant global increase in use of glyphosate, more research is needed to discern the long-term effects of glyphosate on microbes in the environment. One possible effect is the selection of resistance to glyphosate. We predicted that recurrent glyphosate exposure would decrease the amount of time it would take for soil microbes to evolve resistance to the herbicide. We tested the hypothesis that the soil bacterium Pseudomonas fluorescens, when exposed to glyphosate, would become increasingly resistant. We conducted an adaptive evolution experiment growing P. fluorescens in various concentrations of glyphosate. Optical density was measured daily, cultures serially diluted and plated on media containing various concentrations of glyphosate. We found that glyphosate resistance evolved with both infrequent and continuous exposure to glyphosate. Fitness experiments were conducted comparing the resistant mutant to the original strain. Surprisingly, production of pigment/siderophore pyoverdin was inhibited when P. fluorescens was plated on media with glyphosate. Work is underway to determine if fitness of P. fluorescens is affected when iron is limiting.
Glyphosate in Roundup Affects Siderophore Synthesis in Pseudomonas fluorescens
Glyphosate is the most widely used broad spectrum herbicide worldwide. Glyphosate use has increased over 15–fold since the introduction of glyphosate resistant (Roundup Ready) crops in 1996. Given this significant global increase in use of glyphosate, more research is needed to discern the long-term effects of glyphosate on microbes in the environment. One possible effect is the selection of resistance to glyphosate. We predicted that recurrent glyphosate exposure would decrease the amount of time it would take for soil microbes to evolve resistance to the herbicide. We tested the hypothesis that the soil bacterium Pseudomonas fluorescens, when exposed to glyphosate, would become increasingly resistant. We conducted an adaptive evolution experiment growing P. fluorescens in various concentrations of glyphosate. Optical density was measured daily, cultures serially diluted and plated on media containing various concentrations of glyphosate. We found that glyphosate resistance evolved with both infrequent and continuous exposure to glyphosate. Fitness experiments were conducted comparing the resistant mutant to the original strain. Surprisingly, production of pigment/siderophore pyoverdin was inhibited when P. fluorescens was plated on media with glyphosate. Work is underway to determine if fitness of P. fluorescens is affected when iron is limiting.