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Infect. Immun., Jul 1997, 2606-2612, Vol 65, No. 7
B Kenny, A Abe, M Stein and BB Finlay
The pathogenicity of enteropathogenic Escherichia coli (EPEC) is associated
with the expression and secretion of specific bacterial factors. EspB is
one such secreted protein which is required to trigger host signaling
pathways resulting in effacement of microvilli and cytoskeletal
rearrangements. These events presumably contribute to the ensuing diarrhea
associated with EPEC infections. EPEC encounters several environmental
changes and stimuli during its passage from the external environment into
the host gastrointestinal tract. In this paper we show that the secretion
of EspB is subject to environmental regulation, and maximal secretion
occurs under conditions reminiscent of those in the gastrointestinal tract.
Thus, secretion is maximal at 37 degrees C, pH 7, and physiological
osmolarity. In addition, maximal secretion requires the presence of sodium
bicarbonate and calcium and is stimulated by millimolar concentrations of
Fe(NO3)3. The secretion of the four other EPEC-secreted proteins appears to
be modulated in a manner similar to that of EspB. Our results also show
that secretion is not dependent on CO2, as originally reported by Haigh et
al. (FEMS Microbiol. Lett. 129: 63-67, 1995), but that CO2 more likely acts
as a component of the medium buffering system, since CO2 dependence was
abolished by the use of alternative buffers.
Copyright © 1997, American Society for Microbiology
Enteropathogenic Escherichia coli protein secretion is induced in response to conditions similar to those in the gastrointestinal tract
Biotechnology Laboratory, University of British Columbia, Vancouver, Canada.
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