BMC Microbiol. 2016 Nov 9;16(1):271.

Pyruvate oxidase of Streptococcus pneumoniae contributes to pneumolysin release.

Bryant JC1, Dabbs RC1, Oswalt KL1, Brown LR1, Rosch JW2, Seo KS3, Donaldson JR4, McDaniel LS5, Thornton JA6.

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Abstract

BACKGROUND:

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.

RESULTS:

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 H2O2 failed 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.

CONCLUSIONS:

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.

KEYWORDS:

Cytotoxicity; Metabolism; Pneumococcus; Pneumolysin; Protein secretion; Streptococcus pneumoniae; Toxin; Virulence

PMID: 27829373 PMCID: PMC5103497 DOI: 10.1186/s12866-016-0881-6

[PubMed - in process]