DIVOBIS

Microorganisms have a central role in soil biogeochemical processes. Essential functions include nutrient cycling, controlling greenhouse gas fluxes and supporting crop productivity. Soil is one of the most diverse habitats in the biosphere. High throughput sequencing has enabled characterisation of microbial communities, and determination of drivers such as climate and land use are well underway. However, we are only beginning to recognise the scale of viral diversity in soil, and importantly, the impacts of virus-host interactions on key soil biogeochemical cycles and subsequent functional consequences on ecosystems are unknown. Viruses have a range of life strategies, including infection and lysis of host cells or integration followed by lysis, facilitating horizontal transfer of genes and augmentation of function. When a host is lysed, cell contents are released into the labile organic matter pool. In marine systems, 40% of prokaryotes are lysed per day, releasing 150 Gt carbon per annum. However, there is a paucity of information about the impact of top-down control by viruses on soil populations nor the scale of the viral shunt of nutrients. It is likely that viruses have a major impact on microbial diversity and nutrient cycling, with consequences for ecosystem processes. Here we propose a research programme that not only aims to characterise active viral communities in situ, but advances the state-of-the-art by identifying actual impacts of viruses on selected key biogeochemical processes. Specifically, using a series of soil microcosm incubations utilising 13C stable isotope analysis, high throughput metagenomic and metatranscriptomic approaches, in combination with measurements of soil N and C fluxes, we will characterise, for the first time, active viruses together with direct measurements of their impact on biogeochemical cycles.