Resumen de Modelling bacterial ecological estrategies using an individual-based simulator
Cooperation in the microbial world is a social behaviour difficult to explain in the face of natural selection theory. Yet, when cooperation is consistently maintained within a group, a major transition in individuality can occur: multicellularity. An organism is considered multicellular if the cells that comprise it are not independent of each other but rather form a group that coordinates and communicates, with a resulting behaviour that is determined by the interaction of its fundamental elements. In this thesis, I have investigated some of the different steps that lead to the emergence of multicellularity. Such processes are simulated by means of the individual-based simulator gro throughout a variety of experiments that assume different ecological. gro is designed to reproduce birth and competition among the bacterial cells. This added to the specification of the individual traits and the hereditability of those traits, natural selection results as an emergent process. Thanks to the individual-based models it is possible to study how apparently organized collective behaviour emerges out of the small-scale interactions between the individuals. This thesis has been inspired by the conditions that are required for multicellularity to emerge. Briefly, the process of group formation (Chapter 3), the mechanisms for conflict resolution and the maintenance of cooperation (Chapter 4). Finally, this thesis concludes with the study of the most relevant consequence of multicellularity: division of labour (Chapter 5). Results indicate the possible evolutionary tendencies according to the evolution of the fitness of different bacterial ecological strategies. The global aim of this thesis is therefore not to offer specific predictions but rather understand the general properties of a cooperating collective by determining the minimal conditions for the evolutionary transition of multicellularity. The most relevant contributions include the identification of common principles across some of the simulated processes, namely, that cell competition creates more cohesive cell groups, cooperation requires individual selfishness to thrive and specific local cell coordination can result in the emergence of division of labour in homogeneous cell colonies.
