RNA virus infection reshapes carbon and nitrogen partitioning in a marine diatom.

Viral infection is a significant yet understudied factor influencing microbial interactions and chemical transformations in the ocean. In diatoms, crucial for marine primary production, the impact of viruses on host metabolism and elemental cycling is not well understood. This study examined how infection by a lytic single-stranded RNA virus alters carbon (C) and nitrogen (N) fluxes in the nanoplanktonic diatom Mediolabrus comicus.

By using controlled infection experiments combined with flow cytometry, electron microscopy, PAM fluorimetry, and stable isotope probing, researchers observed infection-induced alterations from the population level to the individual cell. Infection triggered immediate optical changes and cellular modifications, including the formation of membrane-bound viral replication chambers.

These changes were followed by early disruption of cellular functions, notably the impairment of photosystem II and a subsequent drop in photosynthetic carbon fixation. Interestingly, during the late stages of infection, nitrogen uptake remained stable and even increased, suggesting continuous resource acquisition to facilitate viral replication.

This imbalance in metabolism led to fluctuations in cellular ratios and a noticeable decrease in population-level carbon and nitrogen intake due to growth suppression. In summary, this research shows that RNA virus infection in diatoms modifies their carbon and nitrogen metabolism, affecting broader marine chemical cycles. The study underscores the role of diatom RNA viruses in marine biogeochemical processes, with potential implications for primary production and organic matter decomposition in the ocean.