The Molecular Basis of Diatom Adhesion and Motility

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Diatoms are unicellular algae that are responsible for ~20% of the global primary biomass production, and are thus of enormous ecological importance. Many diatoms have the remarkable ability to adhere to any natural and man-made surface underwater and move along the surfaces through gliding. In contrast to the well characterized mechanism for underwater adhesion of mussels, the adhesion of diatoms is independent of dopa-containing proteins. Diatoms produce a protein containing, carbohydrate-rich adhesive material (AM), which is secreted through a specialized slit in the cell wall (termed raphe) and deposited as trails on the substratum. The AM provides the necessary traction, while the force for cell motility is generated by an intracellular actin-myosin system. The actin-myosin system is hypothesized to be connected to the extracellular AM trails via a continuum of intracellular and transmembrane proteins. So far, the molecular composition of the diatom AM and the associated components of the actin-myosin based motility system has remained poorly characterized. Based our recent experimental advances we aim to identify in this project the complete set of proteins of the adhesion-motility complex in Craspedostauros australis, which is an established model organism for diatom adhesion. The work in this project will involve proteomics and bioinformatics analyses, molecular genetic manipulation, as well as adhesion and motility assays to identify and functionally characterize the proteins involved in diatom adhesion and motility. The results will provide fundamentally new insights into the molecular basis (a) for diatom underwater adhesion, and (b) for generating the force that enables the rapid bidirectional gliding of diatoms on surfaces.