Mechanism of killing of pneumococci by lysozyme.
Lysozyme is abundant in respiratory secretions and may play a role in lung host defenses. Mechanisms by which lysozyme killed Streptococcus pneumoniae, an important respiratory pathogen, were studied. Lysozyme caused optical clearing of pneumococcal suspensions and released fragments containing [3H]choline from their cell walls. Electron micrographs revealed wide-spread cell wall destruction and bacteriolysis. Breakdown of the cell wall appeared to be mediated mostly by the major pneumococcal autolysin, N-acetylmuramoyl-L-alanine amidase, because it was blocked by phosphorylcholine, a specific inhibitor of amidase, or by substitution of ethanolamine for choline in the cell wall. Blockade of amidase did not greatly increase survival of lysozyme-treated pneumococci on blood agar. Pneumococci in which amidase was blocked appeared intact immediately after treatment with lysozyme, but when they were reincubated at 37 degrees C in fresh culture medium they swelled and lysed. Thus, widespread triggering of the major pneumococcal autolysin is not essential for the bactericidal effect of lysozyme.
Department of Medicine, VA, Medical Center, Lexington, KY.
J D
JD
Coonrod
R
R
Varble
K
K
Yoneda
D001433:Bacteriolysis; D002473:Cell Wall / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D009113:Muramidase / Q000378:metabolism*; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000378:metabolism; D010767:Phosphorylcholine / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000648:ultrastructure
D010767:Phosphorylcholine; D009113:Muramidase; D009238:N-Acetylmuramoyl-L-alanine Amidase