Life history diversity in a large group of chloroviruses

Abstract

Microbial viruses affect the ecology and evolution of every environment on earth. Although these effects can play out on a grand scale, to understand them we need to zoom in to virus' life cycle traits. The values of these traits determine a virus' effect on the host population, the trait diversity provides the material for natural selection, and trade-offs between the traits are expected to constrain virus' evolutionary potential. However, due to the difficulty involved in measuring viral life history phenotypes, there are not many studies that characterize their diversity within clades of viruses. In this study, we quantified the life history of 35 chloroviruses from three host range groups (NC64A, Osy, and SAG viruses). We developed methods to efficiently measure adsorption rate, depolarization probability, lysis probability, lysis time, burst size, specific infectivity, and decay. The trait estimates varied between 5 and 75-fold across all the virus strains, with most traits varying substantially both within and across groups. We then used our largest virus group, the NC64A viruses (n = 20), to look for correlations that could signal trade-offs between traits. We found that viruses with high depolarization probabilities also had higher burst sizes, but lower lysis probabilities once depolarized. These correlations were strong, but their mechanistic underpinnings are unclear. We also found a strong correlation between growth rate and survival in the NC64A viruses. Finally, we discovered biphasic or 'tailing' decay in all the chlorovirus groups. The nature and diversity of these traits has large implications for the ecology and evolutionary potential of the chloroviruses, and confirm the importance of studying viral life cycle traits.

Co-evolutionary patterns shown inOstreococcus-virus system from the Western Baltic Sea in freshly isolated hosts and viruses

“…ii) the faster a plaque increases, the faster the virus spreads and iii) the larger the plaque becomes, the stronger the infection is. However, liquid infection assays where host and virus traits are usually identified [48] are needed to validate these assumptions. All of the mentioned characteristics of the infection will affect the infection dynamics within the ecosystem [10] and potential effects on the Ostreococcus populations [49].…”

Simultaneous Giant Virus and Virophage Quantification Using Droplet Digital PCR

“…Furthermore, multiplex ddPCR can be used for exploring evolutionary changes, such as the evolution of virulence or resistance in the interaction between giant virus and virophage over time. Specifically, different isolated populations of giant virus and virophage stemming from different time points or locations of sampling, can be used to assess how giant virus-virophage interaction changed (i.e., quantifying and comparing virion production from combinations of different isolates) [ 3 ], such as is done using flow cytometry for assaying virus life-history traits (e.g., [ 31 ]). In the context of experimental evolution studies, comparison of virus populations isolated from the experiments with ancestral populations (i.e., the virus population that was used to inoculate the experiments) permits measurement of the population average trait changes (e.g., [ 32 ]).…”

Modelling the interactive effects of viral presence and global warming on Baltic Sea ecosystem dynamics

“…There has been evidence that the viral impact on phytoplankton communities is influenced by temperature and sunlight exposure. Previous studies on viral decay found that viral decay rates increased with sunlight exposure (Noble and Fuhrman, 1997;Suttle and Chen, 1992;Lievens et al, 2022). There has also been evidence that the number of infected cells is higher in the absence of light (by night) than in the presence of light (Winter et al, 2004;Derelle et al, 2018), suggesting a connection between viral infection and irradiance.…”