Previous Article | Next Article ![]()
Appl. Environ. Microbiol., 09 1996, 3088-3093, Vol 62, No. 9
LT Smith
Listeria monocytogenes is a food-borne pathogen that is widely distributed
in nature and is found in many kinds of fresh and processed foods. The
pervasiveness of this organism is due, in part, to its ability to tolerate
environments with elevated osmolarity and reduced temperatures. Previously,
we showed that L. monocytogenes adapts to osmotic and chill stress by
transporting the osmolyte glycine betaine from the environment and
accumulating it intracellularly (R. Ko, L. T. Smith, and G. M. Smith, J.
Bacteriol. 176:426-431, 1994). In the present study, the influence of
various environmental conditions on the accumulation of glycine betaine and
another osmolyte, carnitine, was investigated. Carnitine was shown to
confer both chill and osmotic tolerance to the pathogen but was less
effective than glycine betaine. The absolute amount of each osmolyte
accumulated by the cell was dependent on the temperature, the osmolarity of
the medium, and the phase of growth of the culture. L. monocytogenes also
accumulated high levels of osmolytes when grown on a variety of processed
meats at reduced temperatures. However, the contribution of carnitine to
the total intracellular osmolyte concentration was much greater in samples
grown on meat than in those grown in liquid media. While the amount of each
osmolyte in meat was less than 1 nmol/mg (fresh weight), the overall levels
of osmolytes in L. monocytogenes grown on meat were about the same as those
in liquid samples, from about 200 to 1,000 nmol/mg of cell protein for each
osmolyte. This finding suggests that the accumulation of osmolytes is as
important in the survival of L. monocytogenes in meat as it is in liquid
media.
Copyright © 1996, American Society for Microbiology
Role of osmolytes in adaptation of osmotically stressed and chill- stressed Listeria monocytogenes grown in liquid media and on processed meat surfaces
Department of Agronomy and Range Science, University of California, Davis 95616, USA. lsmith@ucdavis.edu
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»