[1] Inst Pasteur, Mol Genet Unit, F-75724 Paris 15, France
[2] Inst Pasteur, CNRS, URA2172, F-75724 Paris 15, France
[3] FORTH, Inst Mol Biol & Biotechnol, GR-71110 Iraklion, Crete, Greece
[4] Univ Crete, GR-71110 Iraklion, Crete, Greece
[5] Univ Texas, Sch Med, Dept Microbiol & Mol Genet, Houston, TX 77030 USA
[6] Univ British Columbia, Dept Microbiol & Immunol, Vancouver, BC V6T 1Z3, Canada
[7] John Innes Ctr Plant Sci Res, Dept Mol Microbiol, Norwich NR4 7UH, Norfolk, England
[8] Univ Miami, Miller Sch Med, Dept Microbiol & Immunol, Miami, FL 33101 USA