Enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) are diarrheagenic pathotypes of E. coli that cause gastrointestinal disease with the potential
for life-threatening sequelae. While certain EHEC and EPEC virulence mechanisms have
been extensively studied, the factors that mediate host colonization remain to be properly
defined. Previously, we identified four genes (ehaA, ehaB, ehaC, and ehaD) from the prototypic EHEC strain EDL933 that encode for proteins that belong to the autotransporter (AT)
family. Here we have examined the prevalence of these genes, as well as several other
AT-encoding genes, in a collection of EHEC and EPEC strains. We show that the complement of AT-encoding genes in EHEC and EPEC strains is variable, with some AT-encoding
genes being highly prevalent. One previously uncharacterized AT-encoding gene, which we
have termed ehaJ, was identified in 12/44 (27%) of EHEC and 2/20 (10%) of EPEC strains.
The ehaJ gene lies immediately adjacent to a gene encoding a putative glycosyltransferase
(referred to as egtA). Western blot analysis using an EhaJ-specific antibody indicated that
EhaJ is glycosylated by EgtA. Expression of EhaJ in a recombinant E. coli strain, revealed
EhaJ is located at the cell surface and in the presence of the egtA glycosyltransferase
gene mediates strong biofilm formation in microtiter plate and flow cell assays. EhaJ also
mediated adherence to a range of extracellular matrix proteins, however this occurred
independent of glycosylation. We also demonstrate that EhaJ is expressed in a wild-type
EPEC strain following in vitro growth. However, deletion of ehaJ did not significantly alter
its adherence or biofilm properties. In summary, EhaJ is a new glycosylated AT protein
from EPEC and EHEC. Further studies are required to elucidate the function of EhaJ in
colonization and virulence.