Mechanisms of growth and survival in freshwater oligotrophs (MEGASO).

Financial support: Czech Science Foundation (GACR); Project No.: 25-15813S, Duration: 2025-2027

Principal Investigator: Michaela Salcher

Team Members: Clafy Fernandes, Markus Haber, Cecilia Chiriac, Rohit Ghai, Ievgen Lebeda, Alžběta Férová

Growth and survival of highly abundant freshwater oligotrophs adapted to low nutrient conditions are not well understood. We plan to study these mechanisms by comparing them to fast-growing copiotrophs. We will systematically compare strains from three oligotrophic model genera (‘Ca. Fonsibacter’, ‘Ca. Planktophila’, ‘Ca. Methylopumilus’) to meso- and copiotrophs from our large culture collection based on genomic and growth characteristics. Lab experiments combined with seasonal and diurnal metatranscriptomics will identify growth limitations and in situ gene expression to pinpoint fundamental reasons for the overall success of oligotrophs in lakes. We will further investigate a widespread strategy for harvesting light energy, rhodopsin-based photoheterotrophy, by monitoring seasonal and diurnal changes, experiments, and co-expression analyses to identify potential benefits. Finally, we address one of the main mortality factors of aquatic microbes in experiments aiming to resolve the long-standing conundrum if oligotrophs are less affected from grazing by protists than copiotrophs.

This project aims to reveal the mechanisms of growth and survival in freshwater oligotrophs. We will use culture experiments and environmental metatranscriptomics to study their growth limitations, in situ gene transcription, benefits of light-driven rhodopsins, and mortality due to grazing.