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Applied and Environmental Microbiology, November 1999, p. 5023-5027, Vol. 65, No. 11
Departments of Chemical
Engineering2 and
Bioengineering,1 University of
Washington, Seattle, Washington 98195
Received 18 June 1999/Accepted 6 August 1999
Single-copy gene fusions between the lacZ reporter gene
and Escherichia coli strains containing promoters induced
by cold shock (cspA), cytoplasmic stress (ibp),
or protein misfolding in the cell envelope (P3rpoH) were
constructed and tested to determine their ability to detect
antibacterial agents while simultaneously providing information on
their cellular targets. Antibiotics that affect prokaryotic ribosomes
selectively induced the cspA::lacZ or
ibp::lacZ gene fusion, depending on
their mode of action. The membrane-damaging peptide polymyxin B induced
both the P3rpoH::lacZ and
ibp::lacZ fusions, while the
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Stress Responses as a Tool To Detect and
Characterize the Mode of Action of Antibacterial Agents
-lactam antibacterial agent carbenicillin activated only the
P3rpoH promoter. Nalidixic acid, a compound that causes DNA
damage, downregulated
-galactosidase synthesis from
P3rpoH but had little effect on expression of the reporter
enzyme from either the cspA or ibp promoter.
All model antibiotics could be identified over a wide range of
sublethal concentrations with signal-to-noise ratios between 2 and 11. A blue halo assay was developed to rapidly characterize the modes of
action of antibacterial agents by visual inspection, and this assay was
used to detect chloramphenicol secreted into the growth medium of
Streptomyces venezuelae cultures. This simple system holds
promise for screening natural or combinatorial libraries of
antimicrobial compounds.
*
Corresponding author. Mailing address: Department of
Chemical Engineering, University of Washington, P.O. Box 351750, Seattle, WA 98195-1750. Phone: (206) 685-7659. Fax: (206) 685-3451. E-mail: baneyx{at}cheme.washington.edu.
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