Seminari di gruppo IV

Andrea De Martino, "Collective behaviour of cell populations"




It is a basic fact of life that biological populations on any scale, from large natural ecosystems to small microbial communities, are diverse, display diverse behaviours and engineer diverse habitats. Diversity at large scales normally evokes ideas about the way in which selection and evolution can amplify heterogeneity via e.g. the efficient exploitation of resources (`niches’). Somehow, though, when one goes down to the scales of `sparse’ cell collectives, diversity seems to be tied almost entirely to the `intrinsic’ stochasticity of sub cellular processes. It is clearly possible that, at some intermediate scale of life, diversity crosses over from being functionally driven to being, well, `mostly randomness’. On the other hand, revealing functional drives at single-cell level is in general very hard, and one should at least consider the possibility that diversity in cell populations has a more complex origin. My goal is to show that, in one important case involving both bacteria and mammalian cells, this is indeed so: population diversity at metabolic level can be understood as an emergent phenomenon, is predictable, and bears several of the hallmarks of phase transitions found e.g. in magnetic materials. Not too surprisingly, the toolboxes of statistical physics and information theory suffice to bring these aspects to light. Unraveling their numerous biological implications may however require new experimental approaches to the study of cell populations.