  Cellular appendages such as cilia and flagella represent universal tools
enabling cells and microbes, among other essential functionalities, to propel
themselves in diverse environments. In its planktonic, i.e. freely swimming,
state the unicellular bi-flagellated microbe Chlamydomonas reinhardtii employs
a periodic breaststroke-like flagellar beating to displace the surrounding
fluid. Another flagella-mediated motility mode is observed for
surface-associated Chlamydomonas cells, which glide along the surface by means
of force transduction through an intraflagellar transport machinery.
Experiments and statistical motility analysis demonstrate that this gliding
motility enhances clustering and supports self-organization of Chlamydomonas
populations. We employ Minkowski functionals to characterize the spatiotemporal
organization of the surface-associated cell monolayer. We find that simulations
based on a purely mechanistic approach cannot capture the observed non-random
cell configurations. Quantitative agreement with experimental data however is
achieved when considering a minimal cognitive model of the flagellar
mechanosensing.
