Regulation of the Bacterial Cell Wall: Isolation and Characterization of Peptidoglycan Mutants of Staphylococcus aureus1

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RESUMO

Temperature-sensitive mutants of Staphylococcus aureus H which require 1.0 m NaCl for growth at 42 C can be divided into two major classes. Most of the mutants (class A) do not accumulate nucleotide precursors of cell wall biosynthesis in the absence of salt at the nonpermissive temperatures, whereas the class B mutants accumulate these precursors. The most extensively studied mutant RUS 1 (carrying peg-1) is defective in biosynthesis of peptidoglycan at the nonpermissive conditions as evidenced by: (i) reduced incorporation of cell wall precursors into peptidoglycan; (ii) accumulation of the nucleotide, uridine diphosphate (UDP) muramyl-l-alanyl-d-glutamic acid; (iii) reduced specific activity of UDP N-acetylmuramyl (MurNAc)-l-alanyl-d-glutamate: l-lysine ligase (EC 6.3.2.7); and (iv) an increased susceptibility to lysis with sodium dodecyl sulfate. Addition of 1.0 m NaCl reverses these defects with the exception of the specific activity of UDP-MurNAc-l-alanyl-d-glutamate: l-lysine ligase. Nevertheless, the structure of the cell wall is normal at the nonpermissive conditions if 1.0 m NaCl is present. An alteration in the binding of a fluorescent dye, 8-anilino-1-napthalene-4-sulfonic acid at the nonpermissive conditions in the absence of 1.0 m NaCl suggests that there may also be defects in the membrane in this strain.

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