title: Microbial community responses to atrazine exposure and nutrient availability: linking degradation capacity to community structure.
abstract: Repeated pesticide exposure may enhance biodegradation through selective enrichment of pesticide-metabolizing microorganisms, particularly when the compound is used as a C and energy source. The relationship between pesticide application history and degradation rate is unclear when the chemical is utilized as a nutrient source other than C. Atrazine, a poor source of C and energy, was chosen as a model compound because it can serve as an N source for some microorganisms. Soils with (H-soil) and without (NH-soil) prior s-triazine treatment history were repeatedly exposed to atrazine and a variety of C and N source amendments. Exposure to atrazine and inorganic-N availability were the dominant factors leading to the development of microbial communities with an enhanced capacity to degrade atrazine. The density of the atrazine-degrading microorganisms increased immediately, up to 1000-fold, with atrazine exposure in the H-soil, but comparable increases were not observed in the NH-soil until 12 weeks following laboratory acclimation, despite high rates of atrazine mineralization in these soils immediately following the acclimation period. Whole-soil fatty acid methyl ester (FAME) analysis showed that the application of alternative C and N sources in addition to atrazine resulted in a microbial community composition that was distinctly different from that in either the atrazinealone treatment or water controls for both the H- and NH-soils. These data suggest that the microbial communities in both soils were altered differently in response to the treatments but developed a similar enhanced capacity to mineralize atrazine.
authors.affiliation: Delaware Agricultural Experiment Station, Department of Plant and Soil Sciences, College of Agricultural and Natural Resources, University of Delaware, Newark, DE 19717, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Rhine
authors.forename: J J
authors.initials: JJ
authors.lastname: Fuhrmann
authors.forename: M
authors.initials: M
authors.lastname: Radosevich
mesh_terms: D001280:Atrazine / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002244:Carbon / Q000378:metabolism; D006540:Herbicides / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D011157:Population Dynamics; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D006540:Herbicides; D012989:Soil Pollutants; D002244:Carbon; D009584:Nitrogen; D001280:Atrazine