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Applied and Environmental Microbiology, December 1998, p. 4658-4662, Vol. 64, No. 12
Department of Microbiology, Montana State
University, Bozeman, Montana 59717,1 and
Thames Water Utility, Reading RG2 0JN, United
Kingdom2
Received 23 April 1998/Accepted 14 September 1998
Escherichia coli O157:H7 can persist for days to weeks
in microcosms simulating natural conditions. In this study, we used a
suite of fluorescent, in situ stains and probes to assess the influence
of starvation on physiological activity based on membrane potential
(rhodamine 123 assay), membrane integrity (LIVE/DEAD BacLight kit), respiratory activity
(5-cyano-2,3-di-4-tolyl-tetrazolium chloride assay), intracellular
esterase activity (ScanRDI assay), and 16S rRNA content.
Growth-dependent assays were also used to assess substrate
responsiveness (direct viable count [DVC] assay), ATP activity
(MicroStar assay), and culturability (R2A agar assay). In addition,
resistance to chlorine disinfection was assessed. After 14 days of
starvation, the DVC values decreased, while the values in all other
assays remained relatively constant and equivalent to each other.
Chlorine resistance progressively increased through the starvation
period. After 29 days of starvation, there was no significant
difference in chlorine resistance between control cultures that had not
been exposed to the disinfectant and cultures that had been exposed.
This study demonstrates that E. coli O157:H7 adapts to
starvation conditions by developing a chlorine resistance phenotype.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Effects of Starvation on Physiological Activity and
Chlorine Disinfection Resistance in Escherichia coli
O157:H7
*
Corresponding author. Mailing address: Department of
Microbiology, 109 Lewis Hall, Montana State University, Bozeman, MT
59717. Phone: (406) 994-5663. Fax: (406) 994-4926. E-mail:
umbgm{at}montana.edu.
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