Bacteriophages: fantastic little machines for infecting bacteria

Bacteriophages, phages for short, are viruses of bacteria. In ~95% cases their genomic material is a double-stranded DNA, typically 15 microns long, and is packed within a proteinaceous capsid of dimension ~60 microns, at a density of ~500 mg/ml. After a brief introduction to phages, their dimensions, structures and infection-initiation phenomenology, I will argue, using in vitro experimental data, that the phages maintain a high osmotic pressure within their capsids. This osmotic pressure can be used, along with hydrodynamic input, to eject their genomic material in vitro. The actual infection dynamics - in vivo - is even more curious. For that the phages use the osmotic gradient that the bacteria need to maintain across their cell membranes for growth. The very mechanism that allows bacteria to grow, thus, also becomes their Achilles heel.

Debabrata Panja and Ian J. Molineux, "Dynamics of Bacteriophage Genome Ejection In Vitro and In Vivo", Phys. Biol. 7, 045006 (2010).

Ian J. Molineux and Debabrata Panja, "Popping the Cork: Mechanisms of Phage Genome Ejection", Nature Reviews Microbiology 11, 194-204 (2013).

Serge G. Lemay, Debabrata Panja and Ian J. Molineux, "Role of Osmotic and Hydrostatic Pressures in Bacteriophage Genome Ejection", Phys. Rev. E 87, 022714 (2013).