Tunable living bacterial networks: A multi-scaled description of their self-assembly and mechanical behaviour

Abstract

AbstractBioflocculation is increasingly viewed as an alternative path towards bacterial surface colonisation and biofilm formation. This process garners less attention in the literature; however, it is important for wastewater treatment and clinical applications, and has a high potential to be exploited for producing living materials. In this work, we present an aggregating bacterial system that passively forms 3D networks. We apply the toolbox of colloidal physics to control and tune the microstructure and mechanics of the bacterial networks. We firstly augment the cell length distribution of this system by inducing filamentation via oxygen depletion. Filamentation enables the tuning of network properties, enhances aggregation, and reduces the number density required for 3D network assembly. Secondly, we tune the mechanical properties of the bacterial networks through hydrophobation, using glycoside hydrolase enzymes. This approach enables us to transition across three characteristic yielding modes, reducing and enhancing the network’s mechanical strength. Our experimental findings are complemented by Langevin dynamic simulations, which provide insights into the controlling mechanism determining network assembly and microstructure. This work establishes a paradigm towards exploiting bacterial self-assembly for the creation of living gels using biological concepts to tune the network properties, with broad applicability within wastewater treatment, industrial bioreactors and living materials.