Role of osmotic and hydrostatic pressures in bacteriophage genome ejection

TL;DR

This paper proposes a model where osmotic and hydrostatic pressures, along with water flow, drive bacteriophage genome ejection both in vitro and in vivo, offering an alternative to energy-based explanations.

Contribution

It introduces a simple pressure-based model for phage genome ejection, emphasizing hydrodynamic flow and osmotic gradients as key mechanisms.

Findings

Hydrodynamic flow driven by osmotic gradients can explain genome ejection.

The model aligns with existing in vitro data.

It suggests a new in vivo mechanism for phage infection.

Abstract

A critical step in the bacteriophage life cycle is genome ejection into host bacteria. The ejection process for double-stranded DNA phages has been studied thoroughly \textit{in vitro}, where after triggering with the cellular receptor the genome ejects into a buffer. The experimental data have been interpreted in terms of the decrease in free energy of the densely packed DNA associated with genome ejection. Here we detail a simple model of genome ejection in terms of the hydrostatic and osmotic pressures inside the phage, a bacterium, and a buffer solution/culture medium. We argue that the hydrodynamic flow associated with the water movement from the buffer solution into the phage capsid and further drainage into the bacterial cytoplasm, driven by the osmotic gradient between the bacterial cytoplasm and culture medium, provides an alternative mechanism for phage genome ejection \textit{in vivo}; the mechanism is perfectly consistent with phage genome ejection \textit{in vitro}.