Proteomic profiling: A novel approach to understanding the biological causes of soil hydrophobicity

This project will provide the foundation for understanding the relationship between the presence and/or absence of (hydrophobic) protein and soil hydrophobicity. The results will contribute to identifying the proteomic dynamics, which influence soil hydrology and structure, and ultimately the ability of soils to absorb water, support biomass growth, store carbon, and to capture and degrade pollutants. Soil hydrophobicity arises from the release of organic compounds by plants and soil microbes and it reduces or eliminates the ability of soils to absorb water. Depending on its severity, affected (environmental and agricultural) soil areas may not absorb water for periods ranging from minutes to months. After eventually wetting, soil hydrophobicity typically returns following dry periods, when soil moisture levels fall below a critical threshold. Its effects include reduced biomass production, inefficient use of irrigation water, preferential leaching of agri-chemicals and enhanced runoff. The latter contributes to increased flooding and soil erosion, which in turn can damage land. Also, soil water repellency is likely to affect microbial mobility and therefore the ability of soils to capture and degrade pollutants. Hydrophobicity is also relevant for carbon sequestration in soil, as it protects soil organic matter against decomposition. Despite these far reaching environmental and (agro-)economic consequences, the fundamental biological causes of soil hydrophobicity and its transient behaviour are not well understood. Addressing these research gaps is now possible through the application of novel experimental approaches in a crossdisciplinary project, bridging the fields of soil microbiology, environmental proteomics, and soil hydrology. The project will examine mainly UK grassland and dune soils with various characteristics and hydrophobicity, in order to determine and correlate (i) presence or accumulation of specific water-repellent proteins with the occurrence and fluctuations in soil hydrophobicity; (iii) temporal soil-derived protein profiles with the occurrence and fluctuations in soil hydrophobicity. It exploits novel analytical techniques, which include (a) hydrophobic protein extraction procedures under extreme conditions which have never been applied to environmental samples, including soils; and (b) novel general methods for extraction of proteins from soils. The project will lead to an understanding of the influence that soil protein have in determining the hydrophobicity of the soil around them and the manner in which hydrophobicity may change as protein profiles change reflecting varying environmental conditions. This knowledge is critical for accurate prediction of occurrence and effects of soil hydrophobicity, especially the transitions between wettable and non-wettable states, and development of optimum and sustainable natural resource management strategies for soil system functioning. The project is particularly relevant and timely in the context of climate predictions for the coming decades, which suggest more prolonged drought periods as well as more intense precipitation events for the UK and many other regions. Such changes in climatic conditions may induce more widespread development of hydrophobicity in soils, which in turn reduces infiltration and water storage and may increase the number of flooding events during intensely wet periods.