Growth and characteristic layering of <i>Myxococcus xanthus</i> active nematic droplets

Myxococcus xanthus is a social bacterium that exhibits nematic interactions in large populations due to its rod-like shape. When starved, the cells collectively bead from surfaces to form 3D droplet-like aggregates known as fruiting bodies, which are comprised of hundreds of thousands of cells and are crucial for sporulation and survival. We find that these aggregates break symmetry and are often elongated in shape with distinctively non-uniform contact angles. Topographical surface height measurements allow us to characterize the disparate axial and radial growth rates of these droplets, which suggest that different mechanisms underly the axial and radial dynamics. We have recently shown that the early growth of fruiting bodies occurs as a series of 2D layers that are seeded at the position of topological defects in the nematic order field.¹ Here, we investigate the role of layering in the axial growth during further stages of fruiting bodies development. By tracking sparsely labelled cells, we also make progress towards understanding constrained 3D cell motion within these dense fruiting bodies.

¹K Copenhagen et. al. 2020, arxiv: 2001.03804