Altered temperature induction sensitivity of the lambda p(R)/cI857 system for controlled gene E expression in Escherichia coli

Cell lysis of Gram-negative bacteria can be efficiently achieved by express ion of the cloned lysis gene E of bacteriophage PhiX174, Gene E expression is tightly controlled by the rightward lambda p(R) promoter and the tempera ture-sensitive repressor cI857 on lysis plasmid pAW12. The resulting empty bacterial cell envelopes, called bacterial ghosts, are currently under inve stigation as candidate vaccines. Expression of gene E is stringently repres sed at temperatures up to 30 degrees C, whereas gene E expression, and thus cell lysis, is induced at temperatures higher than 30 degrees C due to the rmal inactivation of the cI857 repressor. As a consequence, the production of ghosts requires that bacteria have to be grown at 28 degrees C before th e lysis process is induced. In order to reflect the growth temperature of p athogenic bacteria in vivo, it seemed favorable to extend the heal stabilit y of the lambda p(R) promoter/cI857 repressor system, allowing pathogens to grow at 37 degrees C before induction of lysis. In this study we describe a mutation in the lambda p(R) promoter, which allows stringent repression o f gene E expression at temperatures up to 36 degrees C, but still permits i nduction of cell lysis at 42 degrees C. (C) 1999 Federation of European Mic robiological Societies. Published by Elsevier Science B.V. All rights reser ved.