Bacteria Models Track Evolutionary Dynamics

Physicists use computer simulations and simple bacterial models to capture universal elements of evolutionary dynamics. Physical expansion is key to the growth and prosperity of many populations. Expansion into new spatial and geographical territory is evident in many organisms from viral infections and tumor growth to human and animal migration.

A  team of physicists from Massachusetts sought to understand how territorial expansion affects the survival rate of mutations within a population.  

In their simulations, the researchers compared two computational models of population dynamics and explored the differences between the evolving populations that expanded with a linear, flat expansion front and those that expanded with curved front.  The researchers propose that a curved expansion fronts would describe the inland migration after an organism colonizes a coast.

The researchers also developed an experimental model using two Es-cherichia coli (E. coli) strains in a ring pattern on a Petri dish. As imaged below, the strains of E. coli were labeled with green and blue fluorescent proteins, which allowed the researchers to track the population growth and evolutionary dynamics of the competing bacteria strains.

E. coli labeled with green and blue fluorescent proteins
Image Credit: ©2013 American Physical Society
Two bacterial (Es-cherichia coli) strains grown on a Petri dish, labeled respectively with blue and yellow fluorescent proteins. The strains are otherwise identical. The bacteria started in a partial ring shape, allowing the population to grow radially both inwards and outwards.

Gray arrow  "Radial Domany-Kinzel models with mutation and selection," Phys. Rev. E 87, (2013)

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