&Bullet; physics 14, p79
Bacteria-infecting viruses provide a controllable platform to study the spread of a virus in a cell population.
When viruses or bacteria infect an organism, the outcome of the infection depends on how they spread in their host. Researchers have developed many techniques to visualize bacterial expansion. However, viruses are more difficult to study because, unlike bacteria, they cannot survive without the host. An experimental platform for studying virus expansion must be able to study the complex virus-host interactions. A team led by Diana Fusco from the University of Cambridge in Great Britain has now developed and used such a platform to study the waves of virus expansion in an infected cell population  .
Using light microscopy, the team observed how a bacteriophage – a virus that infects bacteria – colonizes a droplet that E. coli. By combining experiments with simulations, they analyzed the waves of virus expansion in the droplet. According to previous models, such waves should be “pulled”, i.e. driven by virus particles at the borders of the region into which the virus penetrates. However, the team found that the simulations that best fit the data included “pushed” shafts. When waves are pushed, the wavefront moves more slowly than the rest of the wave, which means that particles within the infected region rather than those on the periphery drive the expansion.
The result is surprising, since it is known that push waves arise in the presence of cooperative effects. However, viruses do not interact directly with each other. The observation thus implies that an “effective cooperation” between virus particles arises indirectly through feedback mechanisms that are generated by the interaction of virus particles with their bacterial hosts. The researchers say that understanding that viruses use shock waves to spread will help build better models of the growth and evolution of viruses in infected organisms.
– Matteo Rini
Matteo Rini is the editor of physics.
- M. Hunter et al., “Virus-host interactions shape the spread of the virus, which leads to different classes of traveling waves in spatial dimensions.” Phys. Rev. X11, 021066 (2021).