Related Experiment Video

Updated: Mar 13, 2026

Separating Bacteria by Capsule Amount Using a Discontinuous Density Gradient
05:52

Separating Bacteria by Capsule Amount Using a Discontinuous Density Gradient

Published on: January 7, 2019

14.9K

Pyruvate Oxidase as a Critical Link between Metabolism and Capsule Biosynthesis in Streptococcus pneumoniae

Haley Echlin1, Matthew W Frank1, Amy Iverson1

  • 1Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, Tennessee, United States of America.

Plos Pathogens
|October 21, 2016
PubMed

Insights

The pneumococcus

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Metabolic Biochemistry

Background:

  • Hydrogen peroxide (H2O2) production by Streptococcus pneumoniae is linked to antibiotic synergism, inter-bacterial competition, and host cell damage.
  • The role of H2O2 in pneumococcal invasive disease is complex, with conflicting reports on the impact of H2O2-deficient mutants.
  • Previous studies showed varied outcomes for H2O2-deficient mutants in invasive disease, depending on strain and serotype.

Purpose of the Study:

  • To resolve conflicting observations regarding the role of hydrogen peroxide production in pneumococcal pathogenesis.
  • To investigate the mechanism behind the observed attenuation in invasive disease capacity of certain pneumococcal mutants.
  • To determine the relationship between hydrogen peroxide production, capsule formation, and central metabolism in Streptococcus pneumoniae.

Main Methods:

  • Generating spxB mutants defective in hydrogen peroxide production.
  • Analyzing capsule formation in different pneumococcal serotypes with and without spxB.
  • Measuring steady-state cellular levels of acetyl-CoA in wild-type and mutant strains.
  • Investigating the effect of pdhC deletion on acetyl-CoA and capsule levels.
  • Creating and analyzing spxB and lctO double mutants to assess metabolic restoration.

Main Results:

  • The main hydrogen peroxide producing enzyme, SpxB, is essential for capsule formation in a strain-dependent manner, specifically for capsules with acetylated sugars.
  • spxB mutants exhibited significantly lower steady-state cellular levels of acetyl-CoA, indicating a metabolic imbalance.
  • Deletion of pdhC also led to reduced acetyl-CoA levels and phenocopied the capsule deficiency of the spxB mutant.
  • Capsule production and acetyl-CoA levels were restored in the spxB and lctO double mutant, confirming the link between metabolism and capsule synthesis.

Conclusions:

  • The defect in pathogenesis observed in spxB mutants is primarily due to a metabolic imbalance affecting capsule formation, not reduced hydrogen peroxide production.
  • Acetyl-CoA levels are critical for capsule formation in certain Streptococcus pneumoniae serotypes.
  • This study elucidates the intricate connection between central bacterial metabolism and the expression of virulence factors like the capsule.

More Related Videos

Production of Chemicals by Klebsiella pneumoniae Using Bamboo Hydrolysate as Feedstock07:24

Production of Chemicals by Klebsiella pneumoniae Using Bamboo Hydrolysate as Feedstock

Published on: June 29, 2017

9.5K
Functional Complementation Analysis FCA: A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways09:27

Functional Complementation Analysis FCA: A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways

Published on: June 24, 2016

18.3K

Related Concept Videos

Pyruvate Oxidation01:15

Pyruvate Oxidation

After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure that pyruvate can enter the next metabolic pathway so that energy stored in the pyruvate molecules can be harnessed by the cells.
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
170.5K
Fates of Pyruvate01:20

Fates of Pyruvate

Pyruvate is the end product of glycolysis, where glucose is oxidized to pyruvate, simultaneously reducing NAD+ to NADH. Two molecules of ATP are also produced by substrate-level phosphorylation.
In aerobic organisms, pyruvate is metabolized via the citric acid cycle to produce reduced coenzymes NADH and FADH2. These coenzymes are then oxidized in the electron transport chain to produce ATP and, in the process, regenerate the NAD+ and FAD. As seen in some cell types and organisms, fermentation...
12.0K
Biosynthesis in Bacteria01:24

Biosynthesis in Bacteria

Biosynthesis in bacteria is a fundamental anabolic process that generates essential macromolecules, including proteins, nucleic acids, lipids, and polysaccharides. These macromolecules are critical for cellular growth, replication, and function. The process is tightly regulated and energetically linked to catabolic pathways to ensure optimal resource utilization.Biosynthetic pathways begin with precursor metabolites such as pyruvate, acetyl-CoA, and glucose-6-phosphate derived from glycolysis,...
921
Peptidoglycan Synthesis01:28

Peptidoglycan Synthesis

Structure of PeptidoglycanPeptidoglycan is a vital structural component of the bacterial cell wall, providing mechanical strength and shape to the cell. It consists of repeating units of two sugars—N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)—linked by β-1,4 glycosidic bonds. These sugar chains are cross-linked by short peptide chains, forming a mesh-like polymer that surrounds the bacterial plasma membrane.Cytoplasmic Phase – Precursor SynthesisPeptidoglycan...
3.7K
Gram-negative Bacterial Protein Secretion Systems01:17

Gram-negative Bacterial Protein Secretion Systems

Gram-negative bacteria utilize sophisticated protein secretion systems to transport proteins across their double-membrane envelope into the extracellular environment or host cells. Based on their mechanism of action, these systems are classified into one-step and two-step pathways.One-Step Secretion Systems (Types I, III, IV, and VI)One-step secretion systems bypass the periplasm entirely, forming a continuous channel that spans both the inner and outer membranes:Type I Secretion System (T1SS):...
1.3K
Respiration Pathways01:26

Respiration Pathways

Cellular respiration is a fundamental metabolic process that enables organisms to generate energy from organic molecules. One of its central pathways is the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle, which plays a crucial role in energy production and biosynthetic processes.Conversion of Pyruvate to Acetyl-CoAThe pyruvate generated from glycolysis undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex, producing acetyl-CoA, one molecule of NADH, and one...
858