Unlocking the strength of inducible promoters in Gram-negative bacteria
Correspondence Natalie G. Farny, Worcester Polytechnic Institute, Life Sciences and Bioengineering Center, Room 4034, 60 Prescott Street, Worcester, Massachusetts, 01605, USA.
Email: nfarny@wpi.edu
Abstract
Inducible bacterial promoters are ubiquitous biotechnology tools that have a consistent architecture including two key elements: the operator region recognized by the transcriptional regulatory proteins, and the −10 and −35 consensus sequences required to recruit the sigma (σ) 70 subunits of RNA polymerase to initiate transcription. Despite their widespread use, leaky transcription in the OFF state remains a challenge. We have updated the architecture of the lac and tet promoters to improve their strength, control and portability by the adaptation of the consensus −10 and −35 sequence boxes strongly targeted by σ70, incorporation of a strong ribosome binding site recognized broadly by Gram-negative bacteria, and independent control of the transcriptional regulators by constitutive promoters. To test the promoters, we use the far-red fluorescent protein mCardinal, which significantly improves the signal-to-background ratio of promoter measurements over widely utilized green fluorescent proteins. We validate the improvement in OFF state control and inducibility by demonstrating production of the toxic and aggregate-prone cocaine esterase enzyme CocE. We further demonstrate portability of the promoters to additional Gram-negative species Pseudomonas putida and Vibrio natriegens. Our results represent a significant improvement over existing protein expression systems that will enable advances in protein production for various biotechnology applications.
Attogene Kit Used: benzoic acid detection kit Attogene, EZ2013-03