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Journal of Bacteriology, May 2001, p. 2918-2928, Vol. 183, No. 9
Center for Agricultural Biotechnology,
University of Maryland Biotechnology Institute,1
and Department of Chemical Engineering,2
University of Maryland, College Park, Maryland 20742, and U.S.
Army Edgewood Chemical Biological Center, Aberdeen Proving Ground,
Maryland 210103
Received 8 November 2000/Accepted 6 February 2001
Numerous gram-negative bacteria employ a cell-to-cell signaling
mechanism, termed quorum sensing, for controlling gene expression in
response to population density. Recently, this phenomenon has been
discovered in Escherichia coli, and while pathogenic
E. coli utilize quorum sensing to regulate pathogenesis
(i.e., expression of virulence genes), the role of quorum sensing in
nonpathogenic E. coli is less clear, and in particular,
there is no information regarding the role of quorum sensing during the
overexpression of recombinant proteins. The production of autoinducer
AI-2, a signaling molecule employed by E. coli for
intercellular communication, was studied in E. coli W3110
chemostat cultures using a Vibrio harveyi AI-2 reporter
assay (M. G. Surrette and B. L. Bassler, Proc. Natl. Acad.
Sci. USA 95:7046-7050, 1998). Chemostat cultures enabled a study of
AI-2 regulation through steady-state and transient responses to a
variety of environmental stimuli. Results demonstrated that AI-2 levels
increased with the steady-state culture growth rate. In addition, AI-2
increased following pulsed addition of glucose, Fe(III), NaCl, and
dithiothreitol and decreased following aerobiosis, amino acid
starvation, and
isopropyl-
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.9.2918-2928.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Mapping Stress-Induced Changes in Autoinducer AI-2 Production
in Chemostat-Cultivated Escherichia coli K-12
-D-thiogalactopyranoside-induced expression of
human interleukin-2 (hIL-2). In general, the AI-2 responses to several
perturbations were indicative of a shift in metabolic activity or state
of the cells induced by the individual stress. Because of our interest
in the expression of heterologous proteins in E. coli, the
transcription of four quorum-regulated genes and 20 stress genes was
mapped during the transient response to induced expression of hIL-2.
Significant regulatory overlap was revealed among several stress and
starvation genes and known quorum-sensing genes.
*
Corresponding author. Mailing address: Center for
Agricultural Biotechnology, University of Maryland Biotechnology
Institute, University of Maryland, College Park, MD 20742. Phone: (301)
405-4321. Fax: (301) 314-9075. E-mail:
bentley{at}eng.umd.edu.
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