Completely controlable promoters for usage in genetically modified starter cultures

Promoters are targets sequences on the DNA driving initiation of transcription. The strength of the promoter in question ultimately determines the amount of gene product synthesized. Controllable promoters which can be either turned completely of, resulting in no gene product formed, or turned completely on resulting in high production of gene product, is wanted for several purposes in research and in industry. For use in the dairy industry promoters responding to external signals such as change in temperature, or pH or addition of salt, would be desirable.
Temperate phages must contain promoters which can be either open or completely closed, due to their choice of two different life cycles: lytic and lysogenic.
The promoters PL and PR in TP901-1 which are subject to this control was identified in a previous FØTEK 1 supported project. The purpose of the present project is a further molecular characterization of the elements involved in this on/ of control. The promoter, the operator sites and the regulatory proteins involved will be identified by means of mutant isolation and characterization as well as by biochemical analysis.
Specific selections for mutants with altered regulatory protein giving a temperature sensitive or cold sensitive phenotype will be devised. Also mutants will altered response to salt and pH will be screened for.