Investigating the Biophysical Mechanism Behind Mechanotaxis in Myxococcus Xanthus

When Myxococcus xanthus colonies are grown on hydrogels which have been compressed, the colony grows anisotropically, elongated perpendicular to the direction of compression. This mechanotactic phenomenon, first reported in 1942, has been verified using modern techniques and tied to M.xanthus's gliding motility. However, the microscopic mechanism of realignment is not yet understood. Specifically, existing measurements confound growth and motion, and theoretical models do not consider whether cells respond to stiffness gradients or to polymer alignment within the gel. Additionally, the geometry of the compressed gels used yield irregular strain fields. In this work, we have developed an apparatus that allows for precisely controlled gel compression in a rectangular geometry, which produces a symmetric and nearly uniform strain field. With this platform, we can explore the distinction between growth and motion through single-cell resolution timelapse imaging. By using different hydrogels and explicitly controlling for polymer alignment, we can distinguish between stiffness sensing and polymer orientation alignment. Furthermore, this set up allows for dynamical studies of this phenomenon wherein we can observe the real-time cellular response to changes in gel compression.