Affiliation:
1. Center for Food Safety and Department of Food Science and Technology, University of Georgia, Griffin, Georgia 30223-1797
Abstract
ABSTRACT
Strains of enterohemorrhagic
Escherichia coli
(EHEC) serotype O157:H7 produce under stress copious amounts of exopolysaccharide (EPS) composed of colanic acid (CA). Studies were performed to evaluate the association of production of CA with survival of EHEC under adverse environmental conditions. A CA-deficient mutant, M4020, was obtained from a CA-proficient parental strain,
E. coli
O157:H7 W6-13, by inserting a kanamycin resistance gene cassette (
kan
) into
wcaD
and
wcaE
, 2 of the 21 genes required for CA biosynthesis. M4020 was defective in CA production as determined from the ratio of uronic acid to protein (UA/P) of cells grown from 1 to 4 days at 25°C on minimal glucose agar (MGA), MacConkey agar, and sorbitol-MacConkey agar, and by colony morphology on MGA. The results of stress treatment revealed that M4020 was substantially less tolerant to acid (pH 4.5 and 5.5) and heat (55 and 60°C) in comparison to W6-13, indicating that CA confers on
E. coli
O157:H7 a protective effect from the environmental stresses of acid and heat.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
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