Mechanisms, ecological and biogeochemical significance of algicidal activity in marine bacteria – SIGNAL

Marine phytoplankton and heterotrophic bacteria are essential microorganisms whose biological activity shapes the world we live in. Marine phytoplankton are responsible for up to 50% of global primary production, half of which is quickly remineralized by bacteria. Interactions between phytoplankton and bacteria are complex and play a major role in the diversity and activity of these key players of global elemental cycles. Algicidal bacteria - capable of inducing negative effects on phytoplankton, from arrested growth or photosynthesis inhibition to cell lysis – are found in a large variety of marine habitats. Most of the existing knowledge on algicidal bacteria stems from model strains studied for harmful algal bloom control purposes, with little attention to their ecological roles. As a result, the diversity and abundance of marine algicidal bacteria and their impact on microbial diversity, activity, and carbon cycling are still largely unknown, making this topic a critical area for new knowledge in the fields of marine microbial ecology and biogeochemistry. The SIGNAL project aims to determine the mechanisms and the ecological and biogeochemical significance of algicidal activity in marine bacteria. The proposed research combines classical and cutting-edge tools from several disciplines to 1) identify and quantify algicidal bacteria in marine systems, 2) decipher the molecular and cellular processes at play in bacterial attack of phytoplankton, and 3) assess the ecological and biogeochemical impacts of bacterial algicidal activity. This research will lift current limitations in the study of algicidal bacteria and provide unique insight into a cryptic bacterial function. The results generated will contribute to a better global understanding of phytoplankton-bacteria interactions and resulting carbon fluxes and can help improve predictions of marine microbial communities’ response to changing ocean conditions.