Project: Principles that govern small-scale microbial interactions in the ocean

Gordon and Betty Moore Foundation Grant Name: Kay Bidle Investigator Award

Elucidation of the fundamental principles that govern small-scale interactions between viruses and their microbial hosts, microbes and information-containing molecules, and microbes and the ocean environment—and the subsequent manifestation of these interactions on marine ecosystem processes.

Datasets derive from lab-based experiments and field-based observations from the North Atlantic and California Current Ecosystem

Project Summary:

This project aims to elucidate fundamental principles that govern small-scale microbial interactions at the levels of virus-host, cell-environment, and cell-infochemical signals, and their subsequent manifestation onto marine ecosystem pathways. This work serves as a platform to ask specific questions about how microbial interactions are sensed at an extracellular level and, in turn, how these interactions regulate cell fate (via stress acclimation or PCD induction) at the subcellular level and assess the cellular and mechanistic controls on ecosystem dynamics, nutrient flux, and upper ocean biogeochemistry. Research efforts layer a unique blend of novel analytical proxies and cellular response mechanisms onto a larger conceptual framework of ecosystem response. Key research directions are to: elucidate fundamental principles that regulate host-virus interactions; elucidate critical regulators of microbe–environment sensing and response pathways, and cell fate; elucidate how microbe–information molecule interactions structure and imprint on ocean biogeochemistry; assess how microbial behavior and microscale hot spots drive ocean biogeochemistry; and use novel biomarkers of stress and microbial cell death to diagnose microbial interactions and processes.

The combination of our lab-based mechanistic approaches using model systems along with field-based measurements that employ specific biomarkers of the infection process, have uncovered fundamental underlying principles that regulate microbial interactions and the associated ecological and biogeochemical consequences. We found that these processes are regulated by a unique suite of polar lipids, aspects of biomineralization and TEP production, photoperiod and irradiance level of light, the production of dissolved infochemicals (nitric oxide and other reactive oxygen components), a retrenchment of cellular physiology such as activation of the pentose phosphate pathway and at and an ‘interactase’ of proteins in Archaea that revolve around environmental sensing and caspase activity. We also found that these virus traits and combined with specific ecological scenarios (incorporation into aggregates and removal via sinking; differences in host range) are regulating the competitive ecology of viruses in the oceans. We have also found that nature of virus infection in eukaryotic phytoplankton may be fundamentally different than classic models in that it doesn’t follow a classic lytic pathway but rather operates in a more temperate fashion unless a specific environmental trigger serves a ‘trigger switch’ to drive lysis.  

This work has challenged established paradigms in microbial and viral ecology and has generated novel hypotheses on the critical controls of host-virus interactions and how they are manifesting in the oceans. Our improved mechanistic understanding has now allowed us to extend these models into a larger biogeochemical context and begin to model key regions of virus infection in the oceans, based our understanding of the first principles that critically regulate the infection process itself.