Evolutionary Game Theory and Agent-Based Modeling

Caloric restriction, life-history strategies and aging

(P. Sieber, S. Germerodt, S. Schuster)

Aging is an ubiquitous phenomenon observed across most of the tree of life. However, still little is known about which of the physiological changes that occur during aging are due to the aging process itself (i.e. the continuous deterioration of an organisms' functions) and which are adaptations to the aging process. To investigate this important question from an evolutionary point of view, we use an individual-based resource allocation model in which organisms are constantly exposed to an external stressor. The accumulation of damage eventually leads to the death of the organism. Through an evolutionary algorithm we evolve organisms to determine how they should optimally allocate their resources between reducing stress levels through this stressor and reproduction. Analyzing the evolved organisms, we find a very particular regulatory program that sheds new light onto the relevance of previously reported physiological changes during aging for the survival and longevity of organisms. Moreover, this model allows us to explain previously observed links between obesity as well as dietary restriction with life-span and the onset of age-specific diseases.

Mutualistic interactions among nutrient exchanging bacteria

(S.Lang, K. Bohl, S. Schuster and S. Germerodt)

Mutualism is a special case of cooperation in which two or more interacting species benefit each other. Individuals which benefit from the interaction without reciprocating it to the partner are called defectors or cheaters. While intraspecific cooperation has been studied intensively, interspecific cooperation is considered in very few studies. Questions are: Which ecological factors promote the evolution of mutualisms? How is mutualism maintained despite the evolution of cheaters? Using agent-based modeling, mathematical models and evolutionary game theory we study a model system of interacting bacteria which are capable of exchanging nutrients.

(K. Hausmann, S.Lang and S. Germerodt)

Continuing the work for “Mutualistic interactions among nutrient exchanging bacteria” the agent-based simulation is being extended to answer questions not only at the level of single cells but also at the level of cell fusions to clusters. New data and insights, e. g. feedback inhibition, are being integrated to further improve the model. Questions are: Which mechanisms are used by cells to find cooperation partners? Which factors promote the shift from single cells to clusters as Darwinian individuals? How do clusters evolve over time? Agent-based modeling and mathematical models are used to proceed the analysis of cooperating bacteria.

Mathematical modeling of communication between micro-organisms

(S. Werner A. Schroeter, S. Schuster and S. Germerodt),

In the nature there are a few forms of intra- and inter-species signaling between micro-organisms. A specific example are the communication processes during the sexual mating of fungi (in particular, Mucorales). The pheromone trisporic acid has been previously identified as a key player in these processes. A absorbing point to be researched is mutual exchange of intermediates between mating types during the trisporic acid production. Not only the synthesis of trisporic acid is interesting but also its effect on mating and fusion parasitism. For the analysis of this system we use various methods from mathematical biology and bioinformatics, e.g. evolutionary game theory and individual based modeling.

FungiNet Transregio

(S. Dühring and S. Schuster),

The polymorphic yeast Candida albicans and the filamentous fungus Aspergillus fumigatus are the most important life-threatening human pathogenic fungi. Both fungi have developed multiple strategies to attack and evade the human immune system. Using evolutionary game theory and other biomathematics and bioinformatics methods we analyze the struggle between these fungi and the human immune system. For this we study payoff matrices in view of aggressive strategies versus peaceful coexistence. In examining the switch between different Nash equilibria we determine the conditions under which dimorphic fungi make phenotypic transitions and become pathogenic.

Adaptation versus flexibility: ecology of enzyme expression in microorganisms

(A. Lück, L. Klimmasch, S. Germerodt, C. Kaleta),

Due to environmental changes organisms need to find a balance between being adapted optimally to their current environment and reacting fast to its changes. One way to do this is by utilizing preemptive enzymes: enzymes which are without benefit in the present environment but provide an advantage to survival in a changed environment – for example, enzymes for the uptake of carbon sources that are not currently present. Using individual-based modeling we analyze the influence of different environmental factors like quality and duration of availability of various carbon sources on the expression of preemptive enzymes for these nutrients.

Analyzing evolutionary stability of symbiotic procaryotic communities

(B. Schell, W. Gittel and S. Germerodt)

Benjamin works on the agent-based simulation of symbiotic communities of procaryotes for his master's thesis. The use of evolutionary algorithms for the investigation of the development of circadian rhythms is of particular focus in his efforts. Additionally, game-theoretical approaches are used to examine successful cooperation in the presence of selfish individuals.

Automated analysis of gray-scale time-lapse images

(S. Lang and C. Tokarski)

Live-cell imaging of immune cells and microbes like fungi has become a powerful method to determine their number, motility and behavior. Since image aggregation is growing, there is a need of automated analysis tools to overcome the huge amount of data. While images of stained cells can be analyzed with high accuracy, there is still a lack of automated tracking algorithms for gray-scale time-lapse images. In this project we build up a user-friendly software tool to automatically analyze time-lapse images without the need of any staining of cells or microbes. By labeling one image example of a dataset, the tool is able to determine the optimal parameters to detect and track cells automatically. To ensure the ease of use, a graphical user interface is provided as well as a parallelization possibility to deal with large datasets in a short amount of time.

Root-games in woody savanna plants - predicting root-interactions along environmental gradients with evolutionary game-theory

(F. Mock, J. Schleicher, S. Schuster and S. Germerodt)

We wonder why the degree of intermingling of roots of woody plants in savannas varies. Positive effects, like hydraulic-lift or stem-flow, offer an additional availability for water to plants. Therefore root-intermingling could be interpreted as an act of cooperation. But this 'cooperation' also bares disadvantages, because other resources, e.g. soil nutrients, have to be shared between plants with overlapping root systems. Plants have to balance between facilitation (hydraulic-lift, stem-flow) and competition for resources. We expect that the tendency for 'cooperation' may change along environmental gradients of humidity and nutrients.

Links:

VirtualLabs in evolutionary game theory, Microbial cooperation and competition

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