Ice nucleation activity of two Antarctic sea ice bacteriophages PANV1 and OANV1 and the impact of freezing on their infectivity

Viruses constitute a special class of submicron-sized primary biological aerosol particles that are poorly characterized in terms of ice nucleation activity. Only a handful of studies have been performed about virus ice nucleation with the reported activity ranging between temperatures of approximately –14°C and –28°C. Because none of the previously known bacterial ice nucleation proteins are present in viruses, it has been hypothesized that the observed ice nucleation activity likely results from the high crystallinity and polydispersity of the overall structural organization of the virus particle and its subparts. Microbial ice nucleation has been suggested as a survival mechanism to tolerate cold atmospheric conditions but to date no reports exists whether virus infectivity persists during and after the ice nucleation process. In this work, we study the ice nucleation potential of two environmental viruses originating from Antarctic sea ice, PANV1 and OANV1 and describe the preservation of infectivity before and after the ice nucleation process. This is the first study that investigates the ice nucleating activity of viruses with an icosahedral head and a helical tail, which is one of the most common and abundant environmental virus morphotypes. It is possible that freezing in nature protects viruses and other biological ice nucleating particles, making this process an important mechanism contributing to the preservation of their viability in the environment.