VIBES · The impact of the viral shunt and its metabolic landscape on microbial lifestyles and the flow of carbon during algal blooms

The fate of carbon in marine environments is influenced by associations between heterotrophic bacteria and phytoplankton, mediated by chemical communication and metabolic exchange. Deciphering the nature of these associations is critical given the impact of marine plankton on biogeochemical cycling and climate regulation. Viral infection is a prevalent mortality agent of algal blooms in the ocean, leading to massive release of biomass to the dissolved organic matter (DOM) pool, one of the largest global inventories of carbon. This process, termed the viral shunt, is a key ecosystem process, but remains unquantifiable and mechanistically enigmatic. Furthermore, the metabolic composition of the DOM released following viral infection (vDOM) and its role in shaping microbial communities are largely unknown. In the VIBES project, we will disentangle the complexity of the viral shunt, and elucidate its impact on microbial lifestyles (mutualism and pathogenicity) during algal bloom demise. We will generate experimental approaches to study these bacterial lifestyles, and uncover the chemical language that mediates them. Our expertise in marine microbial chemical ecology, using single-cell transcriptomics to quantify host-pathogen interactions, and metabolomics to identify the chemical signals that govern microbial interactions, will pave the way for unprecedented quantification of the viral shunt. We will investigate the molecular and metabolic basis of virus-derived microbial lifestyles and their consequence for the flow of carbon in the ocean, both under controlled lab-based experiments and during complex interactions in the ocean. We will investigate how microbial lifestyles that specialize on vDOM can determine the partitioning of carbon between the dissolved and particulate fractions, representing carbon cycling and export, respectively. Ultimately, VIBES will enable to evaluate the importance of microscale interactions to the cycling of carbon in the ocean.