Survival of low-pH stress by Escherichia coli O157:H7: correlation between alterations in the cell envelope and increased acid tolerance
Article Abstract:
Survival of a nontoxigenic isolate of Escherichia coli O157:H7 at low pH was studied over prolonged time periods for each of three population types: exponential-phase cells, stationary-phase cells and acid-adapted exponential-phase cells. In each of the three populations, prolonged survival at pH 3.0 was observed. Even after three days at pH 3.0, large numbers of survivors from each population were detected. Increased acid tolerance was found to correlate strongly with a decrease in cytoplasmic proton accumulation. Also, this change in proton permeability was correlated with changes in the protein composition of the cell membranes.
Publication Name: Applied and Environmental Microbiology
Subject: Biological sciences
ISSN: 0099-2240
Year: 1999
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Starvation- and stationary-phase-induced acid tolerance in Escherichia coli O157:H7
Article Abstract:
The cells of Escherichia coli O157:H7 in the late log or stationary phase of the growth cycle are more resistant to acid than the cells in other phases of the growth cycle. If the E. coli cells are deprived of nutrients at 25 degree centigrade their acid resistance increases which is probably due to the formation of some protective protein or regulator. This resistance to acid does not depend on the pH the cells are exposed to before being exposed to acid, and it is possible that there are many systems involved in this protective mechanism seen in E. coli O157:H7.
Publication Name: Applied and Environmental Microbiology
Subject: Biological sciences
ISSN: 0099-2240
Year: 1995
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Prevalence and clonal nature of Escherichia coli O157:H7 on dairy farms in Wisconsin
Article Abstract:
A prevalence study was conducted between Mar. and Oct. 1994 to identify the sources of serotype O157:H7 isolates of Escherichia coli in Wisconsin dairy herds. A total of 302 environmental samples were examined, including two drinking water samples. Results suggest that there are several clonal types of serotype O157:H7 isolates in Wisconsin. The data also indicate that there is more than one source of this pathogen in Wisconsin dairy farms.
Publication Name: Applied and Environmental Microbiology
Subject: Biological sciences
ISSN: 0099-2240
Year: 1996
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