Temperature-Dependent Nanomechanics and Topography of Bacteriophage T7

Viruses are nanoscale infectious agents which may be inactivated by heat treatment. The global molecular mechanisms of virus inactivation and the thermally induced structural changes in viruses are not fully understood. In this study, we measured the heat-induced changes in the properties of T7 bacteriophage particles exposed to a two-stage (65°C and 80°C) thermal effect, by using atomic force microscopy (AFM)-based nanomechanical and topographical measurements. We found that exposure to 65°C led to the release of genomic DNA and to the loss of the capsid tail; hence, the T7 particles became destabilized. Further heating to 80°C surprisingly led to an increase in mechanical stability, due likely to partial denaturation of the capsomeric proteins kept within the global capsid arrangement.IMPORTANCE Even though the loss of DNA, caused by heat treatment, destabilizes the T7 phage, its capsid is remarkably able to withstand high temperatures with a more or less intact global topographical structure. Thus, partial denaturation within the global structural constraints of the viral capsid may have a stabilizing effect. Understanding the structural design of viruses may help in constructing artificial nanocapsules for the packaging and delivery of materials under harsh environmental conditions.