Alladi Ramakrishnan Hall

Use of Evolutionary Game Theory for Biochemistry and Microbiology

Prof. Stefan Schuster

Friedrich Schiller University Jena, Germany

Systems biology focusses on the interactions of many constituents in living systems, which may bring about emergent properties. One methodology to study emergent properties in biology is by Evolutionary Game Theory [1, 2]. This is here illustrated by two examples from biochemistry and microbiology:

(1) Microorganisms are often engineered to produce a variety of extracellular enzymes, for example, for producing renewable fuels and in biodegradation of xenobiotics. Productivity is often reduced by "cheater" mutants, which are deficient in exoenzyme production and benefitting from the product provided by the "cooperating" cells. We present a game-theoretical model to analyze population structure and exoenzyme productivity [3]. Our results indicate that microbial strains engineered for exoenzyme production will not normally be outcompeted by cheater mutants.

(2) The polymorphic fungus Candida albicans can cause disease in humans. Host resistance against these infections is mediated by macrophages among others. Two strategies are available for each pathogenic yeast cell: avoiding lysis transiently or forming hyphae and escaping. In dependence on parameter values, two different outcomes can be derived from our game theoretical model: when the difference of the costs of the two strategies is low, all fungal cells inside a macrophage will switch to hyphae, while in the high-cost case, a mixed population of hyphae and yeast cells is the only stable solution [4]. Our results are in agreement with wet-lab results presented by other groups and the model parameters can be estimated from experimental data.

References
1. T. Pfeiffer, S. Schuster: Game-theoretical approaches to studying the evolution of biochemical systems. Trends Biochem. Sci. 30 (2005) 20-25.
2. S. Hummert, K. Bohl, D. Basanta, A. Deutsch, S. Werner, G. Theißen, A. Schroeter, S. Schuster: Evolutionary game theory: cells as players. Mol. Biosyst. 10 (2014) 3044 - 3065
3. S. Schuster, J.-U. Kreft, N. Brenner, F. Wessely, G. Theißen, E. Ruppin and A. Schroeter: Cooperation and cheating in exoenzyme production by microorganisms: Theoretical analysis in view of biotechnological applications. Biotechnol. J. 5 (2010) 751-758.
4. S. Hummert, Ch. Hummert, A. Schröter, B. Hube, S. Schuster: Game theoretical modelling of survival strategies of Candida albicans inside macrophages. J. theor. Biol. 264 (2010) 312-318