Predicting the persistence of chemicals - the significance of microbial diversity, catabolic prevalence and redundancy in naturally derived inocula

Following their use by society, synthetic chemicals used as agrochemicals, pharmaceuticals and veterinary medicines are released into the environment, where there is the potential for them to exert adverse effects on ecosystems and human health. To assess, manage and mitigate these risks we need to understand the factors which control chemical fate and persistence in the environment. Before chemicals can be approved for use, they must undergo regulatory testing to determine the rate and extent of degradation, and their potential to persist in the environment. The current regulatory studies upon which many of these regulatory studies are no longer fit-for-purpose as they were designed to identify chemicals that undergo rapid degradation and offer little or no ability to screen out highly persistent chemicals. In addition, these studies are conducted under standardised laboratory conditions, are limited in scale, and fail to replicate the dynamic nature and complexity of real world environments.

For most chemicals, biodegradation by microbial communities is the key process which determines environmental persistence. Biodegradation rates are determined by complex interplay between environmental parameters and the abundance and functional characteristics of microbial communities. Microbial communities in environmental compartments such as soil, sediment and water are highly diverse, and extremely variable in space and time. Advances in sequencing methodologies have provided new avenues to characterise microbial communities, with metagenomic and meta-transcriptomic approaches providing opportunities to unravel the nature of microbial communities contributing to chemical degradation, and the specific degradation pathways involved.

Recent studies have suggested that there may be substantial seasonal variation in the potential of microbial communities to degrade chemicals within standardised regulatory tests. Evidence suggests this is linked to variation in microbial community composition driven by factors such as temperature and light. This project will investigate interactions between the chemistry of synthetic compounds, the physico-chemical characteristics of environmental compartments, and temperature for determining biodegradation of chemicals. Special attention will be made to unravelling the microbial mechanisms underlying these interactions using 'omic approaches to allow the development of predictive tools and assays that can be integrated into chemical library screening, foster the development of a new generation of regulatory studies that can prioritise on chemical persistence, and understand the prevalence of key catabolic genes responsible for biodegradation and the functional redundancy/ resilience that exists within microbial communities commonly used as inocula for these biodegradation assays.