Pyruvate oxidase of Streptococcus pneumoniae contributes to pneumolysin release.
Streptococcus pneumoniae is one of the leading causes of community acquired pneumonia and acute otitis media. Certain aspects of S. pneumoniae's virulence are dependent upon expression and release of the protein toxin pneumolysin (PLY) and upon the activity of the peroxide-producing enzyme, pyruvate oxidase (SpxB). We investigated the possible synergy of these two proteins and identified that release of PLY is enhanced by expression of SpxB prior to stationary phase growth.



Mutants lacking the spxB gene were defective in PLY release and complementation of spxB restored PLY release. This was demonstrated by cytotoxic effects of sterile filtered supernatants upon epithelial cells and red blood cells. Additionally, peroxide production appeared to contribute to the mechanism of PLY release since a significant correlation was found between peroxide production and PLY release among a panel of clinical isolates. Exogenous addition of H2O2failed to induce PLY release and catalase supplementation prevented PLY release in some strains, indicating peroxide may exert its effect intracellularly or in a strain-dependent manner. SpxB expression did not trigger bacterial cell death or LytA-dependent autolysis, but did predispose cells to deoxycholate lysis.



Here we demonstrate a novel link between spxB expression and PLY release. These findings link liberation of PLY toxin to oxygen availability and pneumococcal metabolism.
Department of Biological Sciences, Mississippi State University, 295 E Lee Blvd., Harned Hall, Rm 219, Mississippi State, MS, 39762, USA.
Joseph C
JC
Bryant
Department of Biological Sciences, Mississippi State University, 295 E Lee Blvd., Harned Hall, Rm 219, Mississippi State, MS, 39762, USA.
Ridge C
RC
Dabbs
Department of Biological Sciences, Mississippi State University, 295 E Lee Blvd., Harned Hall, Rm 219, Mississippi State, MS, 39762, USA.
Katie L
KL
Oswalt
Department of Biological Sciences, Mississippi State University, 295 E Lee Blvd., Harned Hall, Rm 219, Mississippi State, MS, 39762, USA.
Lindsey R
LR
Brown
Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA.
Jason W
JW
Rosch
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
Keun S
KS
Seo
Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS, USA.
Janet R
JR
Donaldson
Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS, USA.
Larry S
LS
McDaniel
Department of Biological Sciences, Mississippi State University, 295 E Lee Blvd., Harned Hall, Rm 219, Mississippi State, MS, 39762, USA. thornton@biology.msstate.edu.
Justin A
JA
Thornton
D001329:Autolysis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002374:Catalase; D004269:DNA, Bacterial / Q000235:genetics; D004847:Epithelial Cells / Q000382:microbiology; D004912:Erythrocytes / Q000382:microbiology; D005798:Genes, Bacterial; D006861:Hydrogen Peroxide / Q000378:metabolism; D010100:Oxygen; D011771:Pyruvate Oxidase / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D013296:Streptococcus pneumoniae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D013301:Streptolysins / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae; D006861:Hydrogen Peroxide; D002374:Catalase; D011771:Pyruvate Oxidase; D010100:Oxygen
Cytotoxicity; Metabolism; Pneumococcus; Pneumolysin; Protein secretion; Streptococcus pneumoniae; Toxin; Virulence