title: Influence of Internal DNA Pressure on Stability and Infectivity of Phage λ.
abstract: Viruses must remain infectious while in harsh extracellular environments. An important aspect of viral particle stability for double-stranded DNA viruses is the energetically unfavorable state of the tightly confined DNA chain within the virus capsid creating pressures of tens of atmospheres. Here, we study the influence of internal genome pressure on the thermal stability of viral particles. Using differential scanning calorimetry to monitor genome loss upon heating, we find that internal pressure destabilizes the virion, resulting in a smaller activation energy barrier to trigger DNA release. These experiments are complemented by plaque assay and electron microscopy measurements to determine the influence of intra-capsid DNA pressure on the rates of viral infectivity loss. At higher temperatures (65-75°C), failure to retain the packaged genome is the dominant mechanism of viral inactivation. Conversely, at lower temperatures (40-55°C), a separate inactivation mechanism dominates, which results in non-infectious particles that still retain their packaged DNA. Most significantly, both mechanisms of infectivity loss are directly influenced by internal DNA pressure, with higher pressure resulting in a more rapid rate of inactivation at all temperatures.
authors.affiliation: Carnegie Mellon University Department of Physics, Pittsburgh, PA 15213, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: Bauer
authors.affiliation: Carnegie Mellon University Department of Physics, Pittsburgh, PA 15213, USA; Lund University Department of Biochemistry and Structural Biology, 221 00 Lund, Sweden. Electronic address: alexe@cmu.edu.
authors.forename: A
authors.initials: A
authors.lastname: Evilevitch
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics* / Q000472:pathogenicity; D002152:Calorimetry, Differential Scanning; D002213:Capsid / Q000502:physiology; D036022:Capsid Proteins / Q000378:metabolism; D042003:DNA Packaging / Q000502:physiology*; D004279:DNA, Viral / Q000235:genetics*; D016679:Genome, Viral / Q000235:genetics; D006358:Hot Temperature; D011312:Pressure / Q000009:adverse effects; D019065:Virus Assembly; D038301:Virus Inactivation
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral
keywords: DNA pressure; capsid stability; differential scanning calorimetry; infectivity; phage lambda