In Candida albicans, expression of the Hwp1 gene has a “fast” phase that is dependent on this compound after a “slow” phase that is independent of this compound. DNA and this compound from the host organism are incorporated into the protective biofilm formed by Pseudomonas aeruginosa. This compound is used for rapid propulsion by (15[1])Rickettsia, Shigella, and Listeria via namesake (15[1])(*) “comet tails” generated through its explosive polymerization. This compound is regulated by the rho GTPases, which may cause it to form lamellipodia or filopodia. The Arp2/3 complex polymerizes this compound’s globular G form to produce its filamentous F form. This compound forms microfilaments, which along with microtubules make up the cytoskeleton. For 10 points, name this protein that alternates with myosin in muscle fibers. ■END■