&Cartridge; physics 15, p.118
The evolution of a bacterial genome under changing drug concentrations reveals memory formation effects and mimics how disordered solids respond to external forces.
Modern medicine forces bacteria to adapt: in response to antibiotic treatment, they either increase in fitness or die out. Whether a bacterial population survives or not depends on a combination of genetics and environment—the concentration of antibiotics—at any given point in time. Now, Suman Das of the University of Cologne and colleagues are simulating the effects of a constantly changing environment on adaptation . Using a model that describes how slow-moving, disordered systems respond to external forces, the researchers find that microbial evolution exhibits hysteresis and memory formation as drug concentrations change. They use analytical methods and numerical simulations to connect these statistical physics concepts to bacterial drug resistance.
The team’s model examines changes in the genetic sequences of a bacterial population. By combining data on bacterial growth rates with statistical tools, the researchers describe how the bacterial genome can store information about current and past drug concentrations. Their simulations start with a genetic sequence optimized for a specific antibiotic concentration. They then follow how the sequence changes when the concentration shifts to a different value. As the concentration increases and then drops to a lower level, the genetic pathway on the down path depends on the changes on the up path. How different the mutation pathways are depends on the speed of the concentration change.
The researchers note that this behavior mimics that of disordered systems driven by external forces, such as B. ferromagnetic materials exposed to magnetic fields or amorphous materials exposed to a shear force. They say that while their approach focuses on the evolution of drug resistance, the framework can be adapted to other problems in evolutionary biology that involve changing environmental parameters.
– Rachel Berkowitz
Rachel Berkowitz is Corresponding Editor for magazine for physics based in Vancouver, Canada.
- SG That et al.“Driven disordered systems approach to biological evolution in changing environments”, physics Rev X 12031040 (2022).