Characterization of cellular wound resistance in the giant ciliate <i>Stentor coeruleus</i>.

Abstract

Resistance to mechanical stress is essential for cells to prevent wounding and maintain structural integrity. This capability is especially critical for free-living single-celled organisms, which routinely encounter mechanical stress from their natural habitats. We investigated <i>Stentor coeruleus</i>, a single-celled ciliate known for its remarkable wound repair capacity, as a model for studying mechanical wound resistance. While previous work focused on wound repair in <i>Stentor</i>, the structures that enable it to resist wounding remain poorly understood. We characterized how <i>Stentor</i> resisted mechanical stress during transit through a microfluidic constriction. Using high-speed imaging, we tracked the transit dynamics of the cells and linked them to wounding outcomes. Larger cells experienced longer transit times in the constriction and were more prone to rupture, often failing to recover shape due to membrane rupture and loss of cytoplasm. To elucidate the role of the <i>Stentor</i> cytoskeleton, we performed drug-mediated disruption of KM fibers, which are microtubule bundles in the <i>Stentor</i> cytoskeleton. Drug-treated cells exhibited an increased likelihood of membrane rupture at the constriction, implicating KM fibers in wound resistance. To investigate the resistance of <i>Stentor</i> cells to hydrodynamic stress, we injected the cells at increasing flow rates through the constriction. Interestingly, cells were more resistant to larger hydrodynamic stresses up to a threshold, potentially due to shear-thinning of the cytoplasm. Together, these results suggest that <i>Stentor</i> relies on both cytoskeletal architecture and cytoplasmic rheology to withstand mechanical stress, offering insights into cellular strategies for wound resistance in the absence of rigid extracellular structures.