Cryopreservation of Paramecium bursaria Chlorella Virus-1 during an active infection cycle of its host

PLoS One. 2019 Mar 14;14(3):e0211755. doi: 10.1371/journal.pone.0211755. eCollection 2019.

Abstract

Best practices in laboratory culture management often include cryopreservation of microbiota, but this can be challenging with some virus particles. By preserving viral isolates researchers can mitigate genetic drift and laboratory-induced selection, thereby maintaining genetically consistent strains between experiments. To this end, we developed a method to cryopreserve the model, green-alga infecting virus, Paramecium bursaria Chlorella virus 1 (PBCV-1). We explored cryotolerance of the infectivity of this virus particle, whereby freezing without cryoprotectants was found to maintain the highest infectivity (~2.5%). We then assessed the cryopreservation potential of PBCV-1 during an active infection cycle in its Chlorella variabilis NC64A host, and found that virus survivorship was highest (69.5 ± 16.5%) when the infected host is cryopreserved during mid-late stages of infection (i.e., coinciding with virion assembly). The most optimal condition for cryopreservation was observed at 240 minutes post-infection. Overall, utilizing the cell as a vehicle for viral cryopreservation resulted in 24.9-30.1 fold increases in PBCV-1 survival based on 95% confidence intervals of frozen virus particles and virus cryopreserved at 240 minutes post-infection. Given that cryoprotectants are often naturally produced by psychrophilic organisms, we suspect that cryopreservation of infected hosts may be a reliable mechanism for virus persistence in non-growth permitting circumstances in the environment, such as ancient permafrosts.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chlorella vulgaris / virology*
  • Cryopreservation* / methods
  • Phycodnaviridae* / pathogenicity
  • Plant Diseases / virology*

Supplementary concepts

  • Paramecium bursaria Chlorella virus 1

Grants and funding

This work was support by grants from the National Science Foundation (NSF-OCE 1829641) and the Gordon & Betty Moore Foundation (#4971) to SWW. Funding for open access to this research was provided by University of Tennessee’s Open Publishing Support Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.