Gene Expression from Plasmids Containing the araBAD Promoter at Subsaturating Inducer Concentrations Represents Mixed Populations

Gene expression from plasmids containing the araBAD promoter can be regulated by the concentration of arabinose in the growth medium. Guzman et al. [Guzman, L.-M., Belin, D., Carson, M. J. & Beckwith, J. (1995) J. Bacteriol. 177, 4121-4130] showed that expression of a cloned gene could be modula...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1997-07, Vol.94 (15), p.8168-8172
Main Authors: Siegele, Deborah A., Hu, James C.
Format: Article
Language:English
Subjects:
Aequorea victoria
Biological Sciences
Cell growth
Cells
Cultured cells
Enzymes
Fluorescence
Gene Expression
Genes
Green Fluorescent Proteins
Histograms
Inductive reasoning
Kinetics
Lac operon
Luminescent Proteins - biosynthesis
Luminescent Proteins - genetics
Membrane transport proteins
Microbiology
Physical growth
Plasmids
Promoter Regions, Genetic
Proteins
Spectrometry, Fluorescence
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Summary:Gene expression from plasmids containing the araBAD promoter can be regulated by the concentration of arabinose in the growth medium. Guzman et al. [Guzman, L.-M., Belin, D., Carson, M. J. & Beckwith, J. (1995) J. Bacteriol. 177, 4121-4130] showed that expression of a cloned gene could be modulated over several orders of magnitude in cultures grown in the presence of subsaturating concentrations of arabinose. We constructed plasmids expressing a fast-folding mutant Aequorea victoria green fluorescent protein from the araBAD promoter to examine the distribution of expressed gene products in individual cells at intermediate induction levels. Microscopic examination of cells grown at low arabinose concentrations shows mixtures of brightly fluorescent and dark cells, suggesting that intermediate expression levels in cultures reflect a population average of induced and uninduced cells. The kinetics of green fluorescent protein induction suggest that this reflects an ``autocatalytic'' induction mechanism due to accumulation of the inducer by active transport. This mechanism, which is analogous to the induction of the lac operon at subsaturating inducer concentrations in lacY+cells, was described 40 years ago by Novick and Weiner [Novick, A. & Weiner, M. (1957) Proc. Natl. Acad. Sci. USA 43, 553-566].
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.94.15.8168