Viral DNA SIP: the isotopic composition of virions is correlated with that of the substrate used for host growth

DNA Stable Isotope Probing is emerging as a powerful tool to study host-virus interactions. Indeed, since all viruses depend on a host for virion production, a link between the isotopic compositions of hosts and the virions they produce is expected. However, stable isotope probing applied to viral DNA has never been evaluated on simple biological models. Here, this method was tested on the bacteriophage T4 and its host Escherichia coli. To validate that E. coli cells cultivated using a substrate enriched in 13C isotope were resulting on the production of 13C-labeled T4 DNA. T4 DNA buoyant density in CsCl gradient was overall higher than the values predicted by a previously established empirical model, highlighting the need to adapt this type of models when analysing modified viral DNA. Moreover, our results show a strong correlation between the proportion of 13C6-D-glucose in the substrate used for host growth and the buoyant density of T4 DNA, validating the use of DNA SIP in viral ecology, to identify viruses infecting hosts with a specific metabolism. ### Competing Interest Statement The authors have declared no competing interest.