XVI International Botanical Congess

Achnanthes longipes attaches to surfaces via extracellular adhesive structures termed stalks. Electron microscopy cryo-techniques preserved the diatom in the native state. High-pressure freezing/freeze substitution (HPF/FS) revealed cellular vesicles involved in deposition of extracellular polymers. A continuous, multi-layered diatotepic layer located between the protoplasm membrane and the frustule was visualized with freeze-fracture/cryo-SEM and by HPF/FS TEM and found involved the adhesive extrusion. Monoclonal antibodies recognized the adhesives intracellularly and within the stalk. Light and 4D microscopy provided data complimentary to electron microscopy provided the basis for proposal of a novel extracellular polymer biogenesis and assembly mechanism in this diatom.