Fig 1. Schematic diagram of the lac-based, IPTG inducible expression cassette in pMTL-YZ2 (A), and the demonstration of its function in C.
acetobutylicum (B) and C. sporogenes (C). A: Schematic diagram of the lac-based, IPTG inducible expression cassette. Key: LacI is the LacI repressor protein gene. LacI binds to the indicated lacO region, blocking transcription from the Pfac promoter. The Pptb promoter (derived from the C. beijerinckii gene encoding phosphotransbutyrylase) directs the transcription of the lacI gene. B and C: IPTG induction of CAT production in of C. acetobutylicum (B) and C. sporogenes (C) harbouring pMTL-YZ2. Circles equate to cells which received no IPTG, squares represents samples from cells that were induced with IPTG. The arrow indicates the time of adding IPTG. Activity is expressed as units of CAT activity per mg of soluble protein.