Glyphosate is one of themost widely used herbicides in agriculture with predictions that 1.35 million metric tons
will be used annually by 2017. With the advent of glyphosate tolerant (GT) cropping more than 10 years ago,
there is now concern for non-target effects on soil microbial communities that has potential to negatively affect
soil functions, plant health, and crop productivity. Although extensive research has been done on short-term response
to glyphosate, relatively little information is available on long-term effects. Therefore, the overall objective
was to investigate shifts in the rhizosphere bacterial community following long-term glyphosate
application on GT corn and soybean in the greenhouse. In this study, rhizosphere soil was sampled from
rhizoboxes following 4 growth periods, and bacterial community composition was compared between glyphosate
treated and untreated rhizospheres using next-generation barcoded sequencing. In the presence or absence
of glyphosate, corn and soybean rhizospheres were dominated by members of the phyla Proteobacteria,
Acidobacteria, and Actinobacteria. Proteobacteria (particularly gammaproteobacteria) increased in relative abundance
for both crops following glyphosate exposure, and the relative abundance of Acidobacteria decreased in response
to glyphosate exposure. Given that some members of the Acidobacteria are involved in biogeochemical