Response across biological scales: from topologically bound sensitivity to cooperative antibiotic resistance

Speaker: Gabriela Martins (University of Michigan)

Date: 1/12/26

Abstract: In biological systems, response to environmental fluctuations is manifested across different scales, from the molecular reaction level to multicellular communities. In this talk, I will explore systems on opposite extremes of this spectrum. At the molecular level, I will show how an arbitrary response in nonequilibrium reaction networks is constrained by fluctuations of a topological variable and enhanced by nonequilibrium driving. When applied to receptor binding models, this result reveals that, as in equilibrium, sensitivity is constrained by a Hill function, while the Hill coefficient can be enhanced by the nonequilibrium driving beyond its equilibrium limit. At the other end of the scale, I will describe how strongly coupled planktonic and biofilm E. faecalis populations respond to antibiotic stress. Resistant strains respond to drug exposure with enzymatic degradation of the antibiotic molecule, notably leading to long-range cooperative interactions within the population. Resistance is experimentally observed to spread through the community by a population inversion effect, characterized by a non-monotonic relation between initial and final fractions of resistant strains. The observations are captured by a simple well-mixed consumer-resource model with competition mediated by resource sharing and cooperation arising from global toxin degradation.