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Applied and Environmental Microbiology, May 2002, p. 2353-2358, Vol. 68, No. 5
0099-2240/02/$04.00+0 DOI: 10.1128/AEM.68.5.2353-2358.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
and Karen J. Miller*
Department of Food Science, The Pennsylvania State University, University Park, Pennsylvania, 16802
Received 27 August 2001/ Accepted 14 February 2002
The pyruvate dehydrogenase multienzyme complex (PDHC) was found to be upregulated by osmotic stress in the osmotolerant pathogen Staphylococcus aureus. Upregulation was detectable in the levels of both activity and protein and was judged to be about fourfold when sodium chloride was used to adjust the water activity (aw) of the growth medium to 0.94. The upregulation of the PDHC was also found to be humectant dependent and was greatest when impermeant, nonmetabolizable humectants were used to adjust aw. Further experiments provided evidence that in addition to osmotic upregulation, the PDHC complex is also subject to catabolite repression, thus providing a possible explanation for the observation that high concentrations of carbohydrates are generally more inhibitory to the growth of this bacterial pathogen than are high concentrations of salts.
Present address: Department of Microbiology and Molecular Genetics, University of TexasHouston Medical School, Houston, TX 77030.
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