[1] Univ Calif San Diego, Div Biol Sci, La Jolla, CA 92093 USA
[2] Leibniz Inst DSMZ German Collect Microorganisms &, D-38124 Braunschweig, Germany
[3] Univ Calif San Diego, Dept Cellular & Mol Med, La Jolla, CA 92093 USA
[4] Univ Calif San Diego, Dept Chem & Biochem, La Jolla, CA 92093 USA
[5] Univ Calif San Diego, Howard Hughes Med Inst, La Jolla, CA 92093 USA