Invited Talk: Getting in shape—unraveling the morphodynamics of microbial collectives

In nature, microorganisms often collectively self-organize into spatially structured communities, with distinct groups of cells occupying distinct spatial domains. This spatial structure plays a pivotal role in influencing diverse biological functions, such as community growth, stability, resilience, and diversity; and yet, how exactly spatial structure emerges in a multicellular microbial community remains poorly understood. In this talk, I will describe my group's use of both experiments and theory to address this gap in knowledge. First, I will describe our studies of proliferating bacteria, in which the competition by different cells for space and resources shapes the structure of the different domains they inhabit. Next, I will describe our studies of motile bacteria, in which the coupling between cellular motility, metabolism, and nutrient transport gives rise to the formation of dense, immotile phases that coexist with less dense, highly motile phases in a manner reminiscent of Motility-Induced Phase Separation (MIPS). Finally, I will describe our studies of how the phenomenology of MIPS itself is dramatically altered by directed motion along chemical gradients as well as by non-reciprocal predator-prey interactions, two features of many natural microbial communities. Taken altogether, our work helps to provide a biophysical basis for understanding the morphodynamics of microbial communities, as well as other forms of active matter, in complex environments.