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J Lab Clin Med. 1991 Sep;118(3):217-24.

Effect of NaCl-induced osmotic stress on intracellular concentrations of glycine betaine and potassium in Escherichia coli, Enterococcus faecalis, and staphylococci.

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1
Department of Internal Medicine, Ohio State University, Columbus 43210.

Abstract

Staphylococci are more salt tolerant than are enterococci or Escherichia coli. They have a more rigid cell wall and higher internal turgor pressure. The mechanisms of NaCl-induced osmotic tolerance among these bacteria were examined by determining the generation of osmoprotective activity of cellular extracts and intracellular concentrations of glycine betaine and potassium (K+) in response to graded amounts of NaCl. Staphylococci as well as E. coli were shown to require choline or glycine betaine to achieve maximal salt tolerance. In response to 0.9 mol/L NaCl, E. coli exhibited a marked increase in osmoprotective activity, a 168-fold rise in glycine betaine, and a 2.3-fold rise in K+. Enterococcus faealis exhibited a small increase in osmoprotective activity, a 9.3-fold increase in glycine betaine, and a twofold increase in K+. In contrast, strains of Staphylococcus aureus, S. epidermidis, and S. saprophyticus were found to have considerably greater osmoprotective activity, glycine betaine, and K+ than other organisms, even in the absence of external osmotic stress. Glycine betaine rose in some strains, but K+ remained virtually unchanged as the concentration of NaCl was increased. The high concentrations of glycine betaine and K+ in staphylococci, even in the absence of osmotic stress, may explain in part their remarkable salt tolerance and high turgor pressure.

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PMID:
1919294
[Indexed for MEDLINE]

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