Affiliation:
1. Center for Agricultural Biotechnology, University of Maryland Biotechnology Institute,1and
2. Department of Chemical Engineering,2University of Maryland, College Park, Maryland 20742, and
3. U.S. Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, Maryland 210103
Abstract
ABSTRACT
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-β-
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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
92 articles.
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