Abstract:

As the most abundant photosynthetic organisms on Earth, the unicellular cyanobacteria Prochlorococcus and Synechococcus are responsible for as much as 50% of carbon fixation in oligotrophic oceans. Viruses (cyanophages) can lyse cyanobacterial cells and inhibit their carbon fixation, serving as critical components of the marine carbon cycle. Previously, we have successfully built mathematical models to describe the distinct life history traits of cyanophages P-HM2 and P-SSP7, showing that the adsorption rate and latent period of P-HM2 are affected by dark whereas those of P-SSP7 are not. However, the host abundances predicted by the initial models were much lower than experimental observations for both phages, suggesting potential mechanisms for the slowdown of host cell lysis. Here, we proposed five potential mechanisms for the slowdown of Prochlorococcus lysis after infection by P-HM2 or P-SSP7 and assessed them by experiments, respectively. The results showed that among the five candidate mechanisms the different eclipse and latent periods, successful adsorption rate as well as the percentage of resistant cells might contribute to this slowdown. We will add these infection parameters assessed by experiments to the initial models so that we can quantitatively describe the population dynamics of P-HM2 and P-SSP7 during competitions under light-dark cycles in a much more precise manner. Altogether, our findings revealed novel mechanisms by which cyanophages regulate cyanobacterial population dynamics and deepen our understanding of cyanobacteria-controlled marine food webs. 

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