In the oceans, lytic viruses (cyanophages) infect the unicellular picocyanobacteria Prochlorococcus and Synechococcus, which are the most abundant photosynthetic organisms on earth. To adapt to daily light-dark cycle, cyanobacteria show diurnal rhythms of gene expression and metabolism. The adsorption of cyanophages to their host cells also exhibits distinct diel-dependent life history traits. The research team led by Prof. Qinglu Zeng investigated how cyanophages use light-dependent and light-independent adsorption strategies to adapt to the natural light-dark cycle, facilitating future work to understand the interaction of cyanophages and cyanobacteria and its influence on marine carbon cycling.

Using lab cultures, the team compared the relative fitness of cyanophages with different dark infection strategies. By competing equal numbers of two cyanophage strains under continuous light or at different times of a light-dark cycle, they found that the time of infection affects the relative fitness of cyanophages with different adsorption strategies and built a mathematical model to describe the infection kinetics of cyanophages with different adsorption strategies. They also unveiled diel infection rhythms of field cyanophage populations in the North Pacific Subtropical Gyre. The findings of this project have led to publications in scientific journals PNAS, mSystems and Microbiome.