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Microbial changes linked to the accelerated degradation of the herbicide atrazine in a range of temperate soils

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ABSTRACT

Accelerated degradation is the increased breakdown of a pesticide upon its repeated application, which has consequences for the environmental fate of pesticides. The herbicide atrazine was repeatedly applied to soils previously untreated with s-triazines for >5 years. A single application of atrazine, at an agriculturally relevant concentration, was sufficient to induce its rapid dissipation. Soils, with a range of physico-chemical properties and agricultural histories, showed similar degradation kinetics, with the half-life of atrazine decreasing from an average of 25 days after the first application to <2 days after the second. A mathematical model was developed to fit the atrazine-degrading kinetics, which incorporated the exponential growth of atrazine-degrading organisms. Despite the similar rates of degradation, the repertoire of atrazine-degrading genes varied between soils. Only a small portion of the bacterial community had the capacity for atrazine degradation. Overall, the microbial community was not significantly affected by atrazine treatment. One soil, characterised by low pH, did not exhibit accelerated degradation, and atrazine-degrading genes were not detected. Neutralisation of this soil restored accelerated degradation and the atrazine-degrading genes became detectable. This illustrates the potential for accelerated degradation to manifest when conditions become favourable. Additionally, the occurrence of accelerated degradation under agriculturally relevant concentrations supports the consideration of the phenomena in environmental risk assessments.

Electronic supplementary material: The online version of this article (doi:10.1007/s11356-017-8377-y) contains supplementary material, which is available to authorized users.

No MeSH data available.


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Non-metric multidimensional scaling plot of the association of bacterial communities with atrazine treatment in the GA_2012 and GS_2012 soils. Each bacterial community is represented by a triangle, originating from the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S). The bacterial communities are based on OTU clustering of the pyrosequencing of 16S rRNA genes. The variables included in the analysis were soil history: set aside (S) or agricultural (A), duration in days under incubation conditions (0 or 120 days) and atrazine treatment, treated (T) or control (C). The similarity ellipses are based on hierarchical clustering shown in the Online Resource 26
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Fig4: Non-metric multidimensional scaling plot of the association of bacterial communities with atrazine treatment in the GA_2012 and GS_2012 soils. Each bacterial community is represented by a triangle, originating from the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S). The bacterial communities are based on OTU clustering of the pyrosequencing of 16S rRNA genes. The variables included in the analysis were soil history: set aside (S) or agricultural (A), duration in days under incubation conditions (0 or 120 days) and atrazine treatment, treated (T) or control (C). The similarity ellipses are based on hierarchical clustering shown in the Online Resource 26

Mentions: Non-metric multidimensional scaling was conducted using ANOSIM to observe clustering of soil samples according to various variables (Fig. 4). The low abundance of trzN relative to the overall number of bacteria present is consistent with the absence of significant clustering between samples based on atrazine treatment (ANOSIM; R 0.08, p 0.25). This is also consistent with analysis by PERMANOVA showing that the variation in the bacterial communities was most affiliated with their duration of incubation (R2 = 0.23, p 0.0001) and soil type (R2 = 0.17, p 0.0002) rather than atrazine treatment (R2 = 0.08, p 0.09).Fig. 4


Microbial changes linked to the accelerated degradation of the herbicide atrazine in a range of temperate soils
Non-metric multidimensional scaling plot of the association of bacterial communities with atrazine treatment in the GA_2012 and GS_2012 soils. Each bacterial community is represented by a triangle, originating from the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S). The bacterial communities are based on OTU clustering of the pyrosequencing of 16S rRNA genes. The variables included in the analysis were soil history: set aside (S) or agricultural (A), duration in days under incubation conditions (0 or 120 days) and atrazine treatment, treated (T) or control (C). The similarity ellipses are based on hierarchical clustering shown in the Online Resource 26
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig4: Non-metric multidimensional scaling plot of the association of bacterial communities with atrazine treatment in the GA_2012 and GS_2012 soils. Each bacterial community is represented by a triangle, originating from the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S). The bacterial communities are based on OTU clustering of the pyrosequencing of 16S rRNA genes. The variables included in the analysis were soil history: set aside (S) or agricultural (A), duration in days under incubation conditions (0 or 120 days) and atrazine treatment, treated (T) or control (C). The similarity ellipses are based on hierarchical clustering shown in the Online Resource 26
Mentions: Non-metric multidimensional scaling was conducted using ANOSIM to observe clustering of soil samples according to various variables (Fig. 4). The low abundance of trzN relative to the overall number of bacteria present is consistent with the absence of significant clustering between samples based on atrazine treatment (ANOSIM; R 0.08, p 0.25). This is also consistent with analysis by PERMANOVA showing that the variation in the bacterial communities was most affiliated with their duration of incubation (R2 = 0.23, p 0.0001) and soil type (R2 = 0.17, p 0.0002) rather than atrazine treatment (R2 = 0.08, p 0.09).Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

Accelerated degradation is the increased breakdown of a pesticide upon its repeated application, which has consequences for the environmental fate of pesticides. The herbicide atrazine was repeatedly applied to soils previously untreated with s-triazines for >5 years. A single application of atrazine, at an agriculturally relevant concentration, was sufficient to induce its rapid dissipation. Soils, with a range of physico-chemical properties and agricultural histories, showed similar degradation kinetics, with the half-life of atrazine decreasing from an average of 25 days after the first application to <2 days after the second. A mathematical model was developed to fit the atrazine-degrading kinetics, which incorporated the exponential growth of atrazine-degrading organisms. Despite the similar rates of degradation, the repertoire of atrazine-degrading genes varied between soils. Only a small portion of the bacterial community had the capacity for atrazine degradation. Overall, the microbial community was not significantly affected by atrazine treatment. One soil, characterised by low pH, did not exhibit accelerated degradation, and atrazine-degrading genes were not detected. Neutralisation of this soil restored accelerated degradation and the atrazine-degrading genes became detectable. This illustrates the potential for accelerated degradation to manifest when conditions become favourable. Additionally, the occurrence of accelerated degradation under agriculturally relevant concentrations supports the consideration of the phenomena in environmental risk assessments.

Electronic supplementary material: The online version of this article (doi:10.1007/s11356-017-8377-y) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus