Affiliation:
1. Produce Safety and Microbiology Research Unit, WRRC/ARS/USDA, 800 Buchanan St., Albany, California 94710
2. Department of Plant Pathology, Russell Laboratories, 1630 Linden Dr., University of Wisconsin-Madison, Madison, Wisconsin 53706
Abstract
ABSTRACT
Numerous
Salmonella enterica
food-borne illness outbreaks have been associated with contaminated vegetables, in particular sprouted seeds, and the incidence of reported contamination has steadily risen. In order to understand the physiology of
S. enterica
serovar Newport on plants, a screen was developed to identify transposon mutants that were defective in attachment to alfalfa sprouts. Twenty independent mutants from a pool of 6,000 were selected for reduced adherence to alfalfa sprouts. Sixty-five percentage of these mutants had insertions in uncharacterized genes. Among the characterized genes were strains with insertions in the intergenic region between
agfB
, the surface-exposed aggregative fimbria (curli) nucleator, and
agfD
, a transcriptional regulator of the LuxR superfamily, and
rpoS
, the stationary-phase sigma factor. Both AgfD and RpoS have been reported to regulate curli and cellulose production and RpoS regulates other adhesins such as pili. The intergenic and
rpoS
mutants were reduced in initial attachment to alfalfa sprouts by 1 log unit compared to the wild type. Mutations of
agfA
, curli subunit, and
agfB
in
S. enterica
serovar Enteritidis differentially affected attachment to plant tissue. The
agfA
mutation was not reduced in ability to attach to or colonize alfalfa sprouts, whereas the
agfB
mutation was reduced. Thus,
agfB
alone can play a role in attachment of
S. enterica
to plant tissue. These results reveal that
S. enterica
genes important for virulence in animal systems are also required for colonization of plants, a secondary host that can serve as a vector of
S. enterica
from animal to animal.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
218 articles.
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