(319g) Bacterial Cells in Cytoskeleton Composites for Living Materials

The cytoskeleton is a network of interconnected polymers that underlies many mechanical properties and processes of cells including cell division, motility, signaling, metabolism, and growth. The cytoskeleton’s structural adaptability stems from the mechanical properties of its biopolymers, including rigid microtubules and semiflexible actin filaments. Actin and microtubules work together and form composite scaffolds that guide the organization of other cellular components, such as organelles and vesicles. Similarly, in tissue engineering, polymer scaffolds are used to facilitate the organization and growth of tissue cells, while in vivo the biopolymer scaffold known as the extracellular matrix supports and connects our cells. However, how the structure and mechanics of biopolymer scaffolds are affected by inclusions such as cells, vesicles, and organelles, has been largely overlooked. Moreover, understanding how cells embedded in fibrous scaffolds are spatially distributed, and how they modify the scaffold structure and mechanics is critical to engineering tissue and living materials. Here, we study how embedded cells can change the structure of cytoskeleton networks, and how the filament rigidity and network mesh size impact this restructuring. To this end, we polymerize composite networks of actin and microtubules of varying concentrations in the presence of fluorescent E. coli cells and image the cells and filaments using multi-spectral confocal microscopy. We quantify the characteristic structural correlation length scales of both the cells and the filamentous network and map the relationship between cell concentration, filament rigidity, network mesh size, and structure. Our preliminary results suggest that both rigidity and mesh size play important roles in the spatial distribution of cells. More specifically, we see a non-monotonic dependence for actin filament connectivity and a monotonic dependence in microtubule filament connectivity on cell density as cell densities increase. Future work will investigate how the presence of the network influences cell growth, which is critical to tissue regeneration technologies and engineering adaptable materials that employ these composite scaffolds.