title: Glyphosate effects on soil rhizosphere-associated bacterial communities.
abstract: Glyphosate is one of the most 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 processes, a decrease in their abundance could lead to significant changes in nutrient status of the rhizosphere. Our results also highlight the need for applying culture-independent approaches in studying the effects of pesticides on the soil and rhizosphere microbial community.
authors.affiliation: Department of Entomology and Plant Pathology, Auburn University, CASIC Building, Auburn, AL 36849, USA. Electronic address: ramsemm@auburn.edu.
authors.forename: Molli M
authors.initials: MM
authors.lastname: Newman
authors.affiliation: Department of Agricultural Sciences, Northwest Missouri State University, 800 University Drive, Maryville, MO 64468, USA.
authors.forename: Nigel
authors.initials: N
authors.lastname: Hoilett
authors.affiliation: School of Environment and Natural Resources, The Ohio State University, 2021 Coffey Road, Columbus, OH 43210, USA.
authors.forename: Nicola
authors.initials: N
authors.lastname: Lorenz
authors.affiliation: School of Environment and Natural Resources, The Ohio State University, 2021 Coffey Road, Columbus, OH 43210, USA.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Dick
authors.affiliation: Department of Biological Sciences, Auburn University, CASIC Building, Auburn, AL 36849, USA.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Liles
authors.affiliation: Ag Spectrum, 428 East 11th Street, DeWitt, IA 52742, USA.
authors.forename: Cliff
authors.initials: C
authors.lastname: Ramsier
authors.affiliation: Department of Entomology and Plant Pathology, Auburn University, CASIC Building, Auburn, AL 36849, USA.
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Kloepper
mesh_terms: D000383:Agriculture; D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000254:growth & development; D004784:Environmental Monitoring; D005998:Glycine / Q000031:analogs & derivatives* / Q000633:toxicity; D006540:Herbicides / Q000633:toxicity*; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D012987:Soil; D000097797:Glyphosate
keywords: 16S rDNA; Bacterial community composition; Glyphosate; Next-generation sequencing; Soil rhizosphere