Journal of Bacteriology, September 1998, p. 4370-4379, Vol. 180, No. 17
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Division of Microbiology,
Received 20 November 1997/Accepted 20 June 1998
Enterohemorrhagic Escherichia coli (EHEC) exhibits a
pattern of localized adherence to host cells, with the formation of
microcolonies, and induces a specific histopathological phenotype
collectively known as the attaching and effacing lesion. The genes
encoding the products responsible for this phenotype are located on a
35-kb pathogenicity island designated the locus of enterocyte
effacement, which is also shared by enteropathogenic E. coli. We have identified an open reading frame (ORF) which is
located upstream of the espA, espB, and
espD genes on the complementary strand and which exhibits high homology to the genes spiB from
Salmonella, yscD from Yersinia, and
pscD from Pseudomonas. Localization studies
showed that the encoded product is present in the
cytoplasmic and inner membrane fractions of EHEC. The construction and
characterization of a recombinant clone containing an in-frame deletion
of this ORF demonstrated that the encoded product is a putative member
of a type III system required for protein secretion. Disruption of this
ORF, designated pas (protein associated with secretion), abolished the secretion of Esp proteins. The mutant adhered only poorly
and lost its capacities to trigger attaching and effacing activity and
to invade HeLa cells. These results demonstrate that Pas is a
virulence-associated factor that plays an essential role in EHEC
pathogenesis.
*
Corresponding author. Mailing address: Division of
Microbiology, GBF-National Research Centre for Biotechnology,
Mascheroder Weg 1, D-38124 Braunschweig, Germany. Phone:
49-531-6181558. Fax: 49-531-6181411. E-mail: cag{at}gbf.de.
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