Date of Award:

8-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Computer Science

Committee Chair(s)

Nicholas Flann

Committee

Nicholas Flann

Committee

Daniel R. Hyduke

Committee

Kyumin Lee

Abstract

Limited environmental resources push life into competition. In terms of microbes, we assume that the only goal is to grow and competition means to grow faster than the peers. Organisms tend to adapt to their environmental conditions and improve their efficiency in using the common resources to grow faster. While different organisms compete they engage into various social behaviors like cooperation to work together towards a common goal, e.g., production of public goods that benefits the entire population. Hence a part of the resources at hand is dedicated to participate in cooperative activities if the cost-to-benefit ratio is less than one. Evolutionary pressures to outcompete encourage the organisms to “cheat” by deploying all its resources for self-growth without exhibiting cooperative traits and yet take the benefits of others’ altruistic actions. Thus cheaters achieve the cost-to-benefit ratio of zero but the rise of cheaters cuts down the ability of the population to produce public goods. To protect itself during the scarcity of public goods, the contributors exhibit different strategies to limit the cheater’s access to the public goods. Thus, the ability to cheat is conditional to excess production of public goods. This drives the population to an equilibrium frequency of cheaters and contributors. Here we develop a multi-scale mathematical model to study the dynamics of intercellular cooperation within microbes. Our results show that, at equilibrium, the cheaters procure relatively reduced benefit from the public goods, thus making their growth rates identical to the contributors.

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