1. Tetracycline induces chiX transcription. 2. chiX base-pair and sequester the lacZ mRNA RBS, which inhibits translation of the mRNA. 3. Arabinose induces chiXR transcription. 4. chiXR base-pair to chiX , which promote degradation of the sRNA. 5. LacZ repression is relieved.

In a strain that constutively expresses chiX but is lacking chiXR, induction with chitobiose only has the effect of inducing transcription from the promoter, and does not remove chiX downregulation.

In a strain deficient in chiX induction with chitobiose has little effect since the chiP RBS is already unregulated.

Data For Our Favorite New Parts:

1. [http://partsregistry.org/Part:BBa_K564012 Main Page] P_chiP(original):lacZ, BBa_K564012 : Promoter of the chitoporin chiP gene fused with lacZ (from [http://partsregistry.org/Part:BBa_I732005 BBa_I732005]) encoding β-galactosidase. Is induced by chitobiose and is regulated by chiX
2. [http://partsregistry.org/Part:BBa_K564013 Main Page] P_chiP(mutated):lacZ, BBa_K564013: Mutated promoter of the chitoporin chiP gene fused with lacZ (from [http://partsregistry.org/Part:BBa_I732005 BBa_I732005]) encoding β-galactosidase. Is induced by chitobiose, but not regulated by chiX

Data For Pre-existing Parts:

1. [http://partsregistry.org/Part:BBa_I732005:Experience Experience] lacZ (encoding beta-galactosidase, full-length), BBa_I732005: This part controlled by the chiP promoter gave blue colonies when grown on chitobiose.
2. [http://partsregistry.org/Part:BBa_I746908:Experience Experience] Inducible pBad/araC promoter, BBa_I746908: We generated an synthetic promoter library (SPL) based on this part. This allows for the generation of a vast number of arabinose inducible promoters of various strengths.

The arabinose promoter was improved both by rationally changing the -10 and the -35 part of the promoter, and randomly by generating an SPL from the wild-type promoter.