Dynamic switching of cell-substrate contact sites allows gliding diatoms to modulate the curvature of their paths

Abstract: The directed motility of unicellular organisms is critical for their survival and ecological success, yet the mechanisms that enable rigid-walled diatoms to dynamically reorient and alter the shape of their trajectories remain poorly understood. Here, we investigate the gliding motility of Craspedostauros australis, a raphid pennate diatom that moves rapidly across submerged surfaces using an intracellular actomyosin motility complex and the secretion of adhesive extracellular polymeric substances strands. Using high-precision single-cell tracking, scanning electron microscopy, interference reflection microscopy and mathematical modelling, we reveal how diatoms achieve diverse path curvatures by dynamically modulating the location of raphe-substrate contact and switching between one- and two-raphe contact gliding. Our results indicate that local curvature variations along the raphes dictate trajectory shapes, with one-raphe branch contact gliding producing highly curved paths, while two-raphe branch contact gliding results in paths of lower curvature. Interference reflection microscopy imaging further confirms that transitions between these gliding modes underlie abrupt changes in path curvature and cell reorientation. This dynamic raphe-switching mechanism is conserved across cell sizes and correctly predicts the increased path curvatures observed in smaller cells according to their more pronounced local raphe curvature. By quantitatively linking raphe geometry, cell-substrate attachment dynamics and motility patterns, our study provides insights into the motility mechanism that allows diatoms to adapt their movement to complex environments. Description: This dataset contains all data files (single cell tracking data, raw SEM images, segmented raphes, calculated raphe curvatures from model, IRM single cell tracking data) and the data analysis scripts to reproduce all panels in the our journal article Dynamic switching of cell-substrate contact sites allows gliding diatoms to modulate the curvature of their paths. Note that we provide our data analysis scripts as jupyter notebooks, to provide a browser-based, easy to run and transparent data analysis pipeline, where each block produces a single panel of our figures. Additionally we provide the mathematical model, which was first published for apicomplexa by Lettermann et al. https://doi.org/10.1073/pnas.2410708121 and was adapted for diatom gliding by L.Lettermann in a very fruitful collaboration with the group of Ulrich Schwarz. Figure 1 - Trackmate single cell tracking data set (csv) of one DDS population, jupyter notebook analysis script, vector graphic (svg) of figure Figure 2 - Tracking data set (csv) of a single cell on DDS coverslip, Tracking data set (csv) of several cell populations on DDS coverslips, jupyter notebook analysis script, vector graphic (svg) of figure Figure 3 - SEM image of C.australis frustule and panel segments, raphe segementation datasets, tracking data set (csv) of several cell populations on DDS coverslips, jupyter notebook analysis script, mathematical model (Mathematica) of diatom motility by L.Lettermann et al., vector graphic (svg) of figure Figure 4 - IRM data of C.australis cell population gliding on DDS treated coverslip, exemplary movie file & raw microscopy data of single cell IRM trajectory in Fig. 5, data analysis script, vector graphic (svg) of figure Figure 5 - SEM raphe segmentation data of C.australis frustules from differently-sized cells (csv), data analysis script, mathematical model (Mathematica) of diatom motility by L.Lettermann et al., vector graphic (svg) of figure MSD - Supplementary mean-squared displacement analysis script (jupyter notebook), DDS population tracking data (csv)