Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin

ABSTRACT Streptococcus pneumoniae and other streptococci produce a greenish halo on blood agar plates referred to as alpha-hemolysis. This phenotype is utilized by clinical microbiology laboratories to report culture findings of alpha-hemolytic streptococci, including S. pneumoniae, and other bacter...

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Autores principales:	Erin McDevitt, Faidad Khan, Anna Scasny, Courtney D. Thompson, Zehava Eichenbaum, Larry S. McDaniel, Jorge E. Vidal
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Streptococcus pneumoniae alpha-hemolysis hemoglobin met-hemoglobin oxidation Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/56f84435c9c14458b2d0761f05ba9ed0
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spelling	oai:doaj.org-article:56f84435c9c14458b2d0761f05ba9ed02021-11-15T15:31:13ZHydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin10.1128/mSphere.01117-202379-5042https://doaj.org/article/56f84435c9c14458b2d0761f05ba9ed02020-12-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphere.01117-20https://doaj.org/toc/2379-5042ABSTRACT Streptococcus pneumoniae and other streptococci produce a greenish halo on blood agar plates referred to as alpha-hemolysis. This phenotype is utilized by clinical microbiology laboratories to report culture findings of alpha-hemolytic streptococci, including S. pneumoniae, and other bacteria. The alpha-hemolysis halo on blood agar plates has been related to the hemolytic activity of pneumococcal pneumolysin (Ply) or, to a lesser extent, to lysis of erythrocytes by S. pneumoniae-produced hydrogen peroxide. We investigated the molecular basis of the alpha-hemolysis halo produced by S. pneumoniae. Wild-type strains TIGR4, D39, R6, and EF3030 and isogenic derivative Δply mutants produced similar alpha-hemolytic halos on blood agar plates, while cultures of hydrogen peroxide knockout ΔspxB ΔlctO mutants lacked this characteristic halo. Moreover, in the presence of catalase, the alpha-hemolysis halo was absent in cultures of the wild-type (wt) and Δply mutant strains. Spectroscopic studies demonstrated that culture supernatants of TIGR4 released hemoglobin-bound heme (heme-hemoglobin) from erythrocytes and oxidized oxy-hemoglobin to met-hemoglobin within 30 min of incubation. As expected, given Ply hemolytic activity and that hydrogen peroxide contributes to the release of Ply, TIGR4Δply and ΔspxB ΔlctO isogenic mutants had significantly decreased release of heme-hemoglobin from erythrocytes. However, TIGR4Δply that produces hydrogen peroxide oxidized oxy-hemoglobin to met-hemoglobin, whereas TIGR4ΔspxB ΔlctO failed to produce oxidation of oxy-hemoglobin. Studies conducted with all other wt strains and isogenic mutants resulted in similar findings. We demonstrated that the so-called alpha-hemolysis halo is caused by the oxidation of oxy-hemoglobin (Fe+2) to a non-oxygen-binding met-hemoglobin (Fe+3) by S. pneumoniae-produced hydrogen peroxide. IMPORTANCE There is a misconception that alpha-hemolysis observed on blood agar plate cultures of Streptococcus pneumoniae and other alpha-hemolytic streptococci is produced by a hemolysin or, alternatively, by lysis of erythrocytes caused by hydrogen peroxide. We noticed in the course of our investigations that wild-type S. pneumoniae strains and hemolysin (e.g., pneumolysin) knockout mutants produced the alpha-hemolytic halo on blood agar plates. In contrast, hydrogen peroxide-defective mutants prepared in four different strains lacked the characteristic alpha-hemolysis halo. We also demonstrated that wild-type strains and pneumolysin mutants oxidized oxy-hemoglobin to met-hemoglobin. Hydrogen peroxide knockout mutants, however, failed to oxidize oxy-hemoglobin. Therefore, the greenish halo formed on cultures of S. pneumoniae and other so-called alpha-hemolytic streptococci is caused by the oxidation of oxy-hemoglobin produced by hydrogen peroxide. Oxidation of oxy-hemoglobin to the nonbinding oxygen form, met-hemoglobin, might occur in the lungs during pneumococcal pneumonia.Erin McDevittFaidad KhanAnna ScasnyCourtney D. ThompsonZehava EichenbaumLarry S. McDanielJorge E. VidalAmerican Society for MicrobiologyarticleStreptococcus pneumoniaealpha-hemolysishemoglobinmet-hemoglobinoxidationMicrobiologyQR1-502ENmSphere, Vol 5, Iss 6 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Streptococcus pneumoniae alpha-hemolysis hemoglobin met-hemoglobin oxidation Microbiology QR1-502
spellingShingle	Streptococcus pneumoniae alpha-hemolysis hemoglobin met-hemoglobin oxidation Microbiology QR1-502 Erin McDevitt Faidad Khan Anna Scasny Courtney D. Thompson Zehava Eichenbaum Larry S. McDaniel Jorge E. Vidal Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin
description	ABSTRACT Streptococcus pneumoniae and other streptococci produce a greenish halo on blood agar plates referred to as alpha-hemolysis. This phenotype is utilized by clinical microbiology laboratories to report culture findings of alpha-hemolytic streptococci, including S. pneumoniae, and other bacteria. The alpha-hemolysis halo on blood agar plates has been related to the hemolytic activity of pneumococcal pneumolysin (Ply) or, to a lesser extent, to lysis of erythrocytes by S. pneumoniae-produced hydrogen peroxide. We investigated the molecular basis of the alpha-hemolysis halo produced by S. pneumoniae. Wild-type strains TIGR4, D39, R6, and EF3030 and isogenic derivative Δply mutants produced similar alpha-hemolytic halos on blood agar plates, while cultures of hydrogen peroxide knockout ΔspxB ΔlctO mutants lacked this characteristic halo. Moreover, in the presence of catalase, the alpha-hemolysis halo was absent in cultures of the wild-type (wt) and Δply mutant strains. Spectroscopic studies demonstrated that culture supernatants of TIGR4 released hemoglobin-bound heme (heme-hemoglobin) from erythrocytes and oxidized oxy-hemoglobin to met-hemoglobin within 30 min of incubation. As expected, given Ply hemolytic activity and that hydrogen peroxide contributes to the release of Ply, TIGR4Δply and ΔspxB ΔlctO isogenic mutants had significantly decreased release of heme-hemoglobin from erythrocytes. However, TIGR4Δply that produces hydrogen peroxide oxidized oxy-hemoglobin to met-hemoglobin, whereas TIGR4ΔspxB ΔlctO failed to produce oxidation of oxy-hemoglobin. Studies conducted with all other wt strains and isogenic mutants resulted in similar findings. We demonstrated that the so-called alpha-hemolysis halo is caused by the oxidation of oxy-hemoglobin (Fe+2) to a non-oxygen-binding met-hemoglobin (Fe+3) by S. pneumoniae-produced hydrogen peroxide. IMPORTANCE There is a misconception that alpha-hemolysis observed on blood agar plate cultures of Streptococcus pneumoniae and other alpha-hemolytic streptococci is produced by a hemolysin or, alternatively, by lysis of erythrocytes caused by hydrogen peroxide. We noticed in the course of our investigations that wild-type S. pneumoniae strains and hemolysin (e.g., pneumolysin) knockout mutants produced the alpha-hemolytic halo on blood agar plates. In contrast, hydrogen peroxide-defective mutants prepared in four different strains lacked the characteristic alpha-hemolysis halo. We also demonstrated that wild-type strains and pneumolysin mutants oxidized oxy-hemoglobin to met-hemoglobin. Hydrogen peroxide knockout mutants, however, failed to oxidize oxy-hemoglobin. Therefore, the greenish halo formed on cultures of S. pneumoniae and other so-called alpha-hemolytic streptococci is caused by the oxidation of oxy-hemoglobin produced by hydrogen peroxide. Oxidation of oxy-hemoglobin to the nonbinding oxygen form, met-hemoglobin, might occur in the lungs during pneumococcal pneumonia.
format	article
author	Erin McDevitt Faidad Khan Anna Scasny Courtney D. Thompson Zehava Eichenbaum Larry S. McDaniel Jorge E. Vidal
author_facet	Erin McDevitt Faidad Khan Anna Scasny Courtney D. Thompson Zehava Eichenbaum Larry S. McDaniel Jorge E. Vidal
author_sort	Erin McDevitt
title	Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin
title_short	Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin
title_full	Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin
title_fullStr	Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin
title_full_unstemmed	Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin
title_sort	hydrogen peroxide production by <named-content content-type="genus-species">streptococcus pneumoniae</named-content> results in alpha-hemolysis by oxidation of oxy-hemoglobin to met-hemoglobin
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/56f84435c9c14458b2d0761f05ba9ed0
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Hydrogen Peroxide Production by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin

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