[1] BROWN UNIV,DIV BIOL & MED,PROVIDENCE,RI 02912
[2] DUPONT CO,DEPT CENT RES & DEV,EXPTL STN,WILMINGTON,DE 19898
[3] UNIV ADELAIDE,DEPT BIOCHEM,ADELAIDE,SA 5001,AUSTRALIA
[4] KAROLINSKA INST,DEPT MICROBIAL GENET,S-10401 STOCKHOLM 60,SWEDEN
[5] WASHINGTON STATE UNIV,DEPT GENET & CELL BIOL,PULLMAN,WA 99164
[6] WASHINGTON STATE UNIV,DEPT MICROBIOL,PULLMAN,WA 99164
[7] PURDUE UNIV,DEPT BIOL SCI,W LAFAYETTE,IN 47907