Impact of Residual Inducer on Titratable Expression Systems

Inducible expression systems are widely employed for the titratable control of gene expression, yet molecules inadvertently present in the growth medium or synthesized by the host cells can alter the response profile of some of these systems. Here, we explored the quantitative impact of these residu...

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Bibliographic Details
Published in:PloS one 2015-09, Vol.10 (9), p.e0137421-e0137421
Main Authors: Afroz, Taliman, Luo, Michelle L, Beisel, Chase L
Format: Article
Language:English
Subjects:
Analysis
Antibiotics
Arabinose
Arabinose - biosynthesis
Arabinose - genetics
Bacterial Proteins - biosynthesis
Bacterial Proteins - genetics
Chemical synthesis
Deoxyribonucleic acid
DNA
E coli
Engineering
Escherichia coli
Flow Cytometry
Gene expression
Gene Expression Regulation, Bacterial
Genetic engineering
Interrogation
L-Arabinose
Lactose
Mathematical models
Methods
Models, Theoretical
Physiological aspects
Plasmids
Promoter Regions, Genetic
Quantitative genetics
Riboswitch - genetics
Sugar
Thiamine
Thiamine - genetics
Thiamine Pyrophosphate - biosynthesis
Thiamine Pyrophosphate - genetics
Vitamin B
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Summary:Inducible expression systems are widely employed for the titratable control of gene expression, yet molecules inadvertently present in the growth medium or synthesized by the host cells can alter the response profile of some of these systems. Here, we explored the quantitative impact of these residual inducers on the apparent response properties of inducible systems. Using a simple mathematical model, we found that the presence of residual inducer shrinks the apparent dynamic range and causes the apparent Hill coefficient to converge to one. We also found that activating systems were more sensitive than repressing systems to the presence of residual inducer and the response parameters were most heavily dependent on the original Hill coefficient. Experimental interrogation of common titratable systems based on an L-arabinose inducible promoter or a thiamine pyrophosphate-repressing riboswitch in Escherichia coli confirmed the predicted trends. We finally found that residual inducer had a distinct effect on "all-or-none" systems, which exhibited increased sensitivity to the added inducer until becoming fully induced. Our findings indicate that residual inducer or repressor alters the quantitative response properties of titratable systems, impacting their utility for scientific discovery and pathway engineering.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0137421