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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.


Percentage of the bacterial community that contain the atrazine-degrading gene trzN in the GA_2012 and GS_2012 soils. The trzN gene was monitored in the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S), 14 days after the second (2) or third application (3) of atrazine to each soil. TrzN was measured in atrazine-treated and control sub-samples. The proportions of the community carrying trzN was normalised against the 16S rRNA gene for each sample. Error bars show the standard error between experimental replicates, n = 6. The significant differences between the proportion of the community containing trzN between treated and control soils are indicated by asterisk (p < 0.05)
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Fig3: Percentage of the bacterial community that contain the atrazine-degrading gene trzN in the GA_2012 and GS_2012 soils. The trzN gene was monitored in the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S), 14 days after the second (2) or third application (3) of atrazine to each soil. TrzN was measured in atrazine-treated and control sub-samples. The proportions of the community carrying trzN was normalised against the 16S rRNA gene for each sample. Error bars show the standard error between experimental replicates, n = 6. The significant differences between the proportion of the community containing trzN between treated and control soils are indicated by asterisk (p < 0.05)

Mentions: It is clear that there is a significantly greater proportion of the bacterial community containing trzN after the second and third application of atrazine in the agricultural soil and after the second application in the set-aside soil (p < 0.05) (Fig. 3). It is also evident that only a small proportion (<0.5%) of the bacterial community contained trzN.Fig. 3


Microbial changes linked to the accelerated degradation of the herbicide atrazine in a range of temperate soils
Percentage of the bacterial community that contain the atrazine-degrading gene trzN in the GA_2012 and GS_2012 soils. The trzN gene was monitored in the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S), 14 days after the second (2) or third application (3) of atrazine to each soil. TrzN was measured in atrazine-treated and control sub-samples. The proportions of the community carrying trzN was normalised against the 16S rRNA gene for each sample. Error bars show the standard error between experimental replicates, n = 6. The significant differences between the proportion of the community containing trzN between treated and control soils are indicated by asterisk (p < 0.05)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig3: Percentage of the bacterial community that contain the atrazine-degrading gene trzN in the GA_2012 and GS_2012 soils. The trzN gene was monitored in the Ganthorpe agricultural soil, GA_2012 (A), and Ganthorpe set-aside soil, GS_2012 (S), 14 days after the second (2) or third application (3) of atrazine to each soil. TrzN was measured in atrazine-treated and control sub-samples. The proportions of the community carrying trzN was normalised against the 16S rRNA gene for each sample. Error bars show the standard error between experimental replicates, n = 6. The significant differences between the proportion of the community containing trzN between treated and control soils are indicated by asterisk (p < 0.05)
Mentions: It is clear that there is a significantly greater proportion of the bacterial community containing trzN after the second and third application of atrazine in the agricultural soil and after the second application in the set-aside soil (p < 0.05) (Fig. 3). It is also evident that only a small proportion (<0.5%) of the bacterial community contained trzN.Fig. 3

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 &gt;5&nbsp;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&nbsp;days after the first application to &lt;2&nbsp;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.