Understanding microbial uptake efficiency through modal decomposition

Flagellar and ciliary flows are ubiquitous among swimming microorganisms – from bacteria to colonial algae – and underpin physical interactions between microbes and their environment, including resource uptake, predation, and particle capture. Despite intense theoretical and experimental research on swimming microorganisms, the essential flow field features governing material transport remain unresolved. In this study, we use proper orthogonal decomposition (POD) to provide a compact description of the measured spatio-temporal flow fields driven by metachronal surface waves of the model colonial microalga Volvox carteri. Combined with a Langevin description of passive particle transport, our work elucidates the fundamental flow field modes that regulate uptake of dissolved and particulate organic matter. Uptake efficiency of a range of reconstructed flow fields are computationally quantified to resolve the influence of these key flow structures on particle transport across the colony surface. Finally, we investigate how different potential metachronal wave structures influence the local and global uptake by the colony.