Diatom gliding is the result of an actin-myosin motility system

Diatoms are a group of unicellular microalgae that are encased in a highly ornamented siliceous cell wall, or frustule. Pennate diatoms haw: bilateral symmetry and many genera possess an elongated slit in the frustule called the raphe, a feature synonymous with their ability to adhere and glide over a substratum, a process little understood. We have used cytoskeleton-disru pting drugs to investigate the roles of actin, myosin, and microtubules in diatom gliding or motility. No effect on diatom gliding was observed using the cytochalasins, known actin inhibitors, or the microtubule-inhibitors or yzalin and nocodiazole. The latrunculins are a new group of anti-actin drug s, and we show here that they are potent inhibitors of diatom gliding, resu lting in the complete disassociation of the raphe-associated actin cables. The recovery of actin staining and motility following latrunculin treatment was extremely fast. Cells exposed to latrunculin for 12 h recovered full f unction and actin staining within 5 sec of the drug being removed, demonstr ating that the molecular components required for this motility system are i mmediately available. Butanedione monoxime (BDM), a known myosin inhibitor, also reversibly inhibited diatom gliding in a manner similar to the latrun culins. This work provides evidence that diatom gliding is based on an acti n/myosin motility system. (C) 1999 Wiley-Liss, Inc.