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Journal of Bacteriology, November 2000, p. 6391-6400, Vol. 182, No. 22
Department of Biological Sciences, Smith
College, Northampton, Massachusetts
Received 17 March 2000/Accepted 31 August 2000
A comparative study was completed to determine the influence of
various environmental stimuli on the transcription of three different
fimbrial operons in Escherichia coli and to determine the
role of the histone-like protein H-NS in this environmental regulation.
The fimbrial operons studied included the pap operon, which
encodes pyelonephritis-associated pili (P pili), the daa operon, which encodes F1845 fimbriae, and the fan operon,
which encodes K99 fimbriae. Using lacZYA transcriptional
fusions within each of the fimbrial operons, we tested temperature,
osmolarity, carbon source, rich medium, oxygen levels, pH, amino acids,
solid medium, and iron concentration for their effects on fimbrial gene expression. Low temperature, high osmolarity, glucose as a carbon source, and rich medium repressed transcription of all three operons. High iron did not alter transcription of any of the operons tested, whereas the remaining stimuli had effects on individual operons. For
the pap and daa operons, introduction of the
hns651 mutation relieved the repression, either fully or
partially, due to low temperature, glucose as a carbon source, rich
medium, and high osmolarity. Taken together, these data indicate that
there are common environmental cues that regulate fimbrial
transcription in E. coli and that H-NS is an important
environmental regulator for fimbrial transcription in response to
several stimuli.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
H-NS Controls pap and daa
Fimbrial Transcription in Escherichia coli in Response to
Multiple Environmental Cues

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Corresponding author. Mailing address: Department of
Biological Sciences, Smith College, Northampton, MA 01063. Phone: (413) 585-3815. Fax: (413) 585-3786. E-mail:
cwhitezi{at}science.smith.edu.
Present address: Whitehead Institute for Genome Research,
Massachusetts Institute of Technology, Cambridge, MA 01239.
Present address: The Center for Blood Research, Boston, MA 02115.
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