(Supported in part by NSF MCD 95-05885 to J.L. Travis). This project is currently in progress and it involves the amoebae-like protozoan Reticulomyxa. We are investigating, in vivo, the relationship between the transport of external particles (bacteria, algae) along the outer surface of the organism and the underlying microtubule cytoskeleton, which also transports internal particles. To achieve these goals the trapping laser is used to stop and displace beads moving along the membrane surface while the underlying Mts are observed by video enhanced LM. In other experiments microtubule bundles within the cytoplasm are severed with the cutting laser. After surgery the cell is then lysed and its microtubule-mediated transport reactivated with biochemical cocktails. The goal here is to determine if the motility of the organelles and/or the surface attached beads is mediated by a microtubule/microtubule sliding mechanism. Orokos, D.D., A.J. DeMarco, R.W. Cole, and J.L. Travis. (1997) Sliding microtubules move organelles in Reticulomyxa. Molec. Biol. Cell 8: