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Infection and Immunity, May 2000, p. 3010-3014, Vol. 68, No. 5
Division of Infectious Diseases,
Massachusetts General Hospital, Boston, Massachusetts
02114,1 and Department of Microbiology
and Molecular Genetics, Harvard Medical School, Boston, Massachusetts
021152
Received 25 October 1999/Accepted 28 January 2000
Two protein pairs in Vibrio cholerae, ToxRS and TcpPH,
are necessary for transcription from the toxT promoter and
subsequent expression of cholera virulence genes. We have previously
shown that transcription of tcpPH in classical strains of
V. cholerae is activated at mid-log-phase growth in
ToxR-inducing conditions, while transcription of tcpPH in
El Tor strains is not. In this study, we showed that while
transcription of tcpPH differs at mid-log-phase growth in
ToxR-inducing conditions between the biotypes, transcription is
equivalently high during growth in AKI conditions. We used
tcpPH::gusA transcriptional fusions
to quantitate expression of tcpPH in each biotype
throughout growth in ToxR-inducing conditions and showed that although
transcription of tcpPH is reduced at mid-log-phase growth
in an El Tor strain, transcription is turned on later in growth to
levels in excess of those in the classical strain (although cholera
toxin is not produced). This suggests that the difference in expression
of cholera virulence factors in response to ToxR-inducing conditions
between the El Tor and classical biotypes of V. cholerae
may be related to the timing of transcription of tcpPH
rather than the absolute levels of transcription.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Classical and El Tor Biotypes of Vibrio
cholerae Differ in Timing of Transcription of tcpPH
during Growth in Inducing Conditions

*
Corresponding author. Mailing address: Division of
Infectious Diseases, Massachusetts General Hospital, 55 Fruit St.,
Boston, MA 02114. Phone: (617) 726-3811. Fax: (617) 726-7416. E-mail: scalderwood{at}partners.org.
Present address: Molecular Circuitry, Inc., King of Prussia, PA 19406.
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