Macroscopic Theory for Evolving Biological Systems Akin to Thermodynamics

Area of Science:

• Cellular biology
• Evolutionary biology
• Theoretical biology

Background:

• Cellular responses to environmental stress involve complex intracellular reaction dynamics.
• Understanding the plasticity, robustness, and evolvability of these responses is crucial for systems biology.

Purpose of the Study:

• To develop a macroscopic theory characterizing biological responses and their fluctuations.
• To investigate the proportionality of cellular component expression changes under stress.
• To link evolutionary constraints to cellular system behavior.

Main Methods:

• Linear approximation of intracellular reaction dynamics.
• Adaptation experiments with bacterial cultures.
• Simulations of cell models.
• Application of fluctuation-response relationships.

Main Results:

• Demonstrated proportional changes in cellular component expression in response to environmental stress, determined by growth rate.
• Observed this proportionality across different bacterial cultures and conditions.
• Showed that evolutionary robustness constrains expression changes along a one-dimensional curve.
• Found that expression changes are proportionally reduced by evolution, similar to Le Chatelier's principle.
• Established proportionality between fluctuations from genetic changes and noise.

Conclusions:

• Cellular systems can be formulated akin to thermodynamics, with growth rate as a macroscopic potential.
• Evolutionary processes shape cellular responses for robustness and adaptability.
• The macroscopic theory provides a framework for understanding biological system behavior.