Interactions between phages and their microbial hosts in soils from wetlands - Consequences on soil organic matter dynamics and greenhouse gas fluxes – PHAWET

Phages, viruses that infect bacteria and archaea, are the most abundant biological entities on Earth. In soils, they can have an impact on greenhouse gas (GHG) fluxes by infecting microorganisms involved in the carbon (C) and nitrogen (N) cycles. However, these phage-host interactions remain poorly documented. PHAWET aims to fill this gap by targeting wetland soils, wetlands being considered to be major ecosystems for storing C in the form of organic matter (SOM), but are in turn sources of methane (CH4) and nitrous oxide (N2O). In these soils, SOM dynamic is regulated by changes in water level. We hypothesise that these changes in soil moisture regulate phage-host diversity, their encounter rates and the phage life cycle. This would have an impact on SOM cycling and GHG fluxes via the acquisition of auxiliary metabolic genes by the hosts and the viral shunt. PHAWET will incorporate field monitoring based on two critical zone observatories (OZCAR) and experiments in soil meso- and microcosms. At these three scales of complexity, we will be studying the dynamics of SOM using innovative analytical (metabolomics) and isotopic tools. The taxonomic and functional diversities of phages and their hosts will be analysed in the soils of two wetlands using 'omics' tools. GHG fluxes induced by changes in water levels in these soils will be measured in undisturbed soil cores, and the effect of soil moisture on phage-host interactions will be assessed in soil microcosms with native communities and model couples of phage and bacteria. By targeting wetland soils, PHAWET will study for the first time the role of soil moisture on phage-host interactions and its consequences on SOM dynamics and GHG fluxes.