Hydrodynamic Modelling and Experiment of Spiroplasma's Cytoskeletal Driven Motility

Nearly all swimming bacteria have evolved to utilize external, helical, rotating appendages called flagella to achieve motility. These flagella are anchored into a cell wall which provides a structural rigidity during the swimming process. Contrary to this, a unique helical bacterium called spiroplasma has neither a cell wall nor flagella, yet still swims in water with a set of unique internal cytoskeletal filaments. These filaments deform thereby deforming the cell’s external barrier, a viscoelastic bilayer lipid membrane. This mechanism allows for motility, yet the interaction between the filaments and spiroplasma’s membrane is unclear. We model this motility using a regularized stokeslet approximation to hydrodynamic interactions and investigate the cell’s ability to deform its membrane using torsion and bend-based modalities. We then use microscopy to compare which model is best suits spiroplasma’s motion.