Affiliation:
1. Department of Food Science and Technology, University of California, Davis, California 95616
Abstract
ABSTRACT
The
food-borne pathogen
Listeria monocytogenes
proliferates at
refrigeration temperatures, rendering refrigeration ineffective in the
preservation of
Listeria
-contaminated foods. The uptake and
intracellular accumulation of the potent compatible solutes glycine
betaine and carnitine has been shown to be a key mediator of the
pathogen's cold-tolerant phenotype. To date, three compatible
solute systems are known to operate in
L. monocytogenes
:
glycine betaine porter I (BetL), glycine betaine porter II (Gbu), and
the carnitine transporter OpuC. We investigated the specificity of each
transporter towards each compatible solute at 4°C by examining
mutant derivatives of
L. monocytogenes
10403S that possess
each of the transporters in isolation. Kinetic and steady-state
compatible solute accumulation data together with growth rate
experiments demonstrated that under cold stress glycine betaine
transport is primarily mediated by Gbu and that Gbu-mediated betaine
uptake results in significant growth stimulation of chill-stressed
cells. BetL and OpuC can serve as minor porters for the uptake of
betaine, and their action is capable of providing a small degree of
cryotolerance. Under cold stress, carnitine transport occurs primarily
through OpuC and results in a high level of cryoprotection. Weak
carnitine transport occurs via Gbu and BetL, conferring correspondingly
weak cryoprotection. No other transporter in
L. monocytogenes
10403S appears to be involved in transport of either compatible solute
at 4°C, since a triple mutant strain yielded neither transport
nor accumulation of glycine betaine or carnitine and could not be
rescued by either osmolyte when grown at that
temperature.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
87 articles.
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