Abstract
Hosts influence and are influenced by viral replication. Cell size, for example, is a fundamental trait for microbial hosts that can not only alter the probability of viral adsorption, but also constrain the host physiological processes that the virus relies on to replicate. This intrinsic connection can affect the fitness of both host and virus, and therefore their mutual evolution. Here, we study the coevolution of bacterial hosts and their viruses by considering the dependence of viral performance on the host physiological state (viral plasticity). To this end, we modified a standard host-lytic phage model to include viral plasticity, and compared the coevolutionary strategies emerging under different scenarios, including cases in which only the virus or the host evolve. For all cases, we also obtained the evolutionary prediction of the traditional version of the model, which assumes a non-plastic virus. Our results reveal that the presence of the virus leads to an increase in host size and growth rate in the long term, which benefits both interacting populations. Our results also show that viral plasticity and evolution influence the classic host quality-quantity trade-off. Poor nutrient environments lead to abundant low-quality hosts, which tends to increase viral infection time. Conversely, richer nutrient environments lead to fewer but high-quality hosts, which decrease viral infection time. Our results can contribute to advancing our understanding of the microbial response to changing environments. For instance, both cell size and viral-induced mortality are essential factors that determine the structure and dynamics of the marine microbial community, and therefore our study can improve predictions of how marine ecosystems respond to environmental change. Our study can also help devise more reliable strategies to use phage to, for example, fight bacterial infections.
Highlights
Cell size is a key trait for microbial systems
We focus on Escherichia coli as host, but our approach can be generalized to any bacterium
Because the dilution rate is positively correlated with nutrient concentration, increasing w leads to bigger hosts in richer environments and, eventually, an emerging size is reached that maximizes host growth
Summary
Cell size is a key trait for microbial systems. Replication rates and physiological traits are generally correlated with cell size, both within and across species (Litchman et al, 2007). The size of the host influences the surface-to-volume ratio, which triggers additional consequences e.g., increasing cell size decreases the diffusion flux per unit cell volume of external nutrient into the cell, but increases internal diffusion rates (Gallet et al, 2017). Both external and internal diffusion rates affect the mobility of intracellular resources used by the host. The latter, among other factors influenced by cell size such as resource uptake, affects the host physiological state. The host physiological state influences the performance of the viral infection (Calendar and Abedon, 2005) and the dynamics of both viral and bacterial populations (Choua and Bonachela, 2019)
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