Mechanical characterization of P2 bacteriophage by using Young’s modulus measurements

Seong Soo Choi,Kyoung Jin Kim

doi:10.1063/5.0035106

Abstract

The bacteriophage P2 capsids have been characterized by transmission electron microscopy and atomic force microscopy (AFM). Studies have been carried out on fully filled and 2/3 filled capsids containing dsDNA genomes. In order to get the quantitative information of the capsid, a nanoindentation technique depending on the tip-shape and an effective spring constant technique with a homogeneous capsid shell model were adopted. The contact region of the AFM contact force curve in an approach mode has been used for the calculation of Young’s moduli as well as the internal pressures of the capsids. By using the continuum theory of elasticity of thin homogeneous capsid shells, Young’s moduli of fully filled and 2/3 filled phage capsids are measured to be 1.17 ± 0.10 GPa and 0.87 ± 0.10 GPa, respectively. These values are close to other reported results. Analysis of the force curves also presented that a fully filled capsid reveals a higher internal pressure than that of a 2/3 filled capsid.

Highlights

There has been a considerable interest toward the bacteriophage due to its various possible applications such as phage-therapy and bio-motors
We examined its geometrical dimensions by atomic force microscopy (AFM) imaging and Young’s moduli of the capsids through force spectroscopy measurements
The images of P2-sized phage samples were presented by transmission electron microscopy (TEM) and AFM

Summary

INTRODUCTION

There has been a considerable interest toward the bacteriophage due to its various possible applications such as phage-therapy and bio-motors. In bacteriophage P2 and bacteriophage P4 systems, the 2/3-filled capsid of P4 ash sid contains two copies of P4 genomes, which is equivalent to about 67% (2/3) of the full genome size of P2 in the P2-sized head This kind of mutant virus particles provided the opportunity to examine the extremely under-packaged and still biologically active phage particle. Understanding physical properties of the fully filled P2-sized capsid and 2/3 filled (under packaged) P2-sized capsid we present in this manuscript would be helpful to figure out how viral genomic DNA is packaged into empty capsid and the packaged capsid is stably maintained Though these two-dimensional structures of the P2-sized capsid are reported to be identical to each other via electron microscopy measurements, the physical properties of its capsid are not clarified yet. After three times of buffer change, each fraction was recovered from

Preparation of the phage stock

TEM measurement

EXPERIMENTAL RESULTS AND DISCUSSION

SUMMARY