How important is soil microbial diversity for pesticide biodegradation function and robust biodegradation kinetics?

Lead Research Organisation: University of Reading
Department Name: Geography and Environmental Sciences


The project will focus on elucidating the relationship between soil biodiversity and pesticide degradation as a function of the soil ecosystem. The vast phylogenetic and functional diversity residing within soil has recently attracted scientific attention regarding its importance for ecosystem function. Existing studies investigating biodiversity-function relationships for soil microorganisms have focussed on the decomposition of natural inputs to soil (e.g. plant litter). The degradation of man-made compounds, such as pesticides, is also facilitated by the soil microbial community and is as such another important function of this ecosystem. Low environmental persistence of pesticides is in turn an important criterion set by the regulatory authorities for the registration and sale of pesticides. To satisfy future demands for modern and effective pesticides, the agrochemical industry strives to develop new compounds with degradation characteristics that are both favourable and robust (quickly and reliably degraded in a wide range of agricultural soils). The key hypothesis underlying this project is that pesticide biodegradation function will depend on soil biodiversity but the nature of the dependence will be a function of the complexity of pesticide chemical structure. The importance of a large pool of catabolic genes from which a degradation pathway may be assembled as well as the importance of the phylogenetic diversity (= donors and recipients of catabolic elements between which the pathway is assembled) equally warrant investigation. A soil microcosm system with an established gradient of reduced microbial diversity will be used to investigate the dependence of degradation on biodiversity. By using a range of compounds of different structural characteristics the project aims to study the relationship between compound chemistry and degradation kinetics under conditions of limited soil biodiversity. Microbial communities will be characterised using phylogenetic profiling as well as quantification of functional markers and relative determination of community complexity. Biodegradation of the 14C-labelled model compounds will be characterized by quantification of parent compound loss, production of metabolites and, where applicable, mineralization. This proposal is the product of genuine interaction between industry and academia. The industrial partner, Syngenta, a world-leading agri-business committed to sustainable agriculture through innovative research, initially approached the academic partner, Shaw, who has unique expertise in pesticide microbiology in the UK. At Syngenta, degradation data is first generated at an early stage of pesticide development and is used to prioritise compounds for further development. A proportion of compounds passing persistence criteria at this high throughput stage subsequently reveal highly variable rates of degradation in more detailed higher tier test systems such as studies using different soils and field trials. The research will improve understanding of the relationship between compound degradation and soil biodiversity; an outcome compatible with Shaw's research aspirations. It will also establish whether the degradation kinetics of a given compound in systems of decreasing biodiversity can be predictive of variable persistence in the field, thus potentially allowing Syngenta to rationalise their compound development workflow. The student will benefit from interdisciplinary scientific training at the interface between molecular microbial ecology and environmental chemistry. The generation and characterization of soil diversity gradients will be conducted at UoR whilst biodegradation studies will be conducted during a placement at Syngenta where, in addition to the broader opportunities for generic and employability skills training within academia, the student will have the opportunity to benefit from business-related training in an industrial research environment.


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