Cooperation and Conflict in Human and Microbial Societies

Verma, Prateek (2019) Cooperation and Conflict in Human and Microbial Societies. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (Phd thesis of Prateek Verma (14RS018)) 14RS018.pdf - Submitted Version Restricted to Repository staff only Download (6MB)

Abstract

Corruption in the form of bribery poses serious economic and social repercussion in many nation states. Harassment bribes are a special class of bribes paid by citizens to acquire a service which otherwise they are legally obligated. A major part of this thesis has focused on understanding the conditions under which harassment bribery can be reduced by using the framework of evolutionary game theory. We specifically looked at the consequences of symmetric (both bribe-giver and taker are held liable) and asymmetric penalty (only the bribe-taker is punished) by developing deterministic and stochastic evolutionary game-theoretic models in well-mixed and network structured populations. We found that asymmetric penalty can lead to reduction in incidents of bribery, but the extent of the reduction depends crucially on the manner in which agents change their strategies over time, the underlying topology, relative size of citizen’s & officer’s sub-population and degree of the inter-dependent social network in which the agents are embedded. We have also investigated the evolutionary dynamics of competition among antibiotic producer, sensitive and degrader cell on a spatially structured population of bacterial community. Antibiotic produced by producer inhibits the growth of sensitive cell. Degraders resist the harmful effect of antibiotic by secreting degradation enzyme which nullifies its effect and shields other neighbouring sensitive cells. Previous studies on this system have ignored the diffusion effect of secreted chemicals by producer and degrader cells. Our study highlighted the essential role of diffusion of antibiotic and degradation enzyme on the stability of coexistence of different strains in a microbial community.

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