Related Experiment Video

Updated: Jun 19, 2026

Implementation of a Permeable Membrane Insert-based Infection System to Study the Effects of Secreted Bacterial Toxins on Mammalian Host Cells
09:25

Implementation of a Permeable Membrane Insert-based Infection System to Study the Effects of Secreted Bacterial Toxins on Mammalian Host Cells

Published on: August 19, 2016

VARIANTS OF HEMOLYTIC STREPTOCOCCI; THEIR RELATION TO TYPE-SPECIFIC SUBSTANCE, VIRULENCE, AND TOXIN

E W Todd1, R C Lancefield

  • 1Hospital of The Rockefeller Institute for Medical Research.

The Journal of Experimental Medicine
|October 30, 2009
PubMed

Insights

Newly isolated hemolytic streptococci exhibit virulent or attenuated matt colony forms. Degradation yields avirulent glossy variants, though some retain traits, impacting bacterial virulence and M substance.

Area of Science:

  • Microbiology
  • Bacteriology
  • Immunology

Background:

  • Freshly isolated hemolytic streptococci form characteristic matt colonies containing type-specific substance M.
  • Two virulent varieties of matt cultures exist: virulent and attenuated.
  • Degradation of matt forms leads to glossy, avirulent variants.

Purpose of the Study:

  • To investigate the characteristics and interconversion of hemolytic streptococci colony variants.
  • To understand the role of type-specific substance M in virulence and colony morphology.
  • To examine the stability and potential reversion of glossy variants.

Main Methods:

  • Isolation of hemolytic streptococci from pathogenic lesions.
  • Cultivation on artificial media and selection of colonies.
  • Cultivation in homologous anti-M serum.
  • Assessment of virulence in mice.
  • Analysis of type-specific substance M content.
  • Evaluation of toxic filtrates' skin reactivity.

Main Results:

  • Matt virulent and matt attenuated varieties of hemolytic streptococci were identified.
  • Degradation via prolonged cultivation, colony selection, or anti-M serum produced glossy, avirulent variants.
  • Glossy variants lost most type-specific substance M, but complete loss was rare.
  • Fully degraded glossy forms were stable, but some retained M substance could revert to matt forms.
  • Toxic filtrates from both matt and glossy cultures showed similar skin reactivity.
  • No correlation was found between bacterial virulence and toxigenicity.

Conclusions:

  • Hemolytic streptococci exhibit distinct colony morphologies (matt and glossy) linked to virulence and M substance content.
  • Environmental or experimental manipulations can induce stable or reversible changes in colony type and virulence.
  • While M substance is crucial for virulence, its partial retention in glossy variants allows for potential reversion.
  • Toxigenicity is independent of virulence and colony type in these streptococcal variants.

More Related Videos

Visualization of Bacterial Toxin Induced Responses Using Live Cell Fluorescence Microscopy14:29

Visualization of Bacterial Toxin Induced Responses Using Live Cell Fluorescence Microscopy

Published on: October 1, 2012

Related Concept Videos

Bacterial Toxins01:12

Bacterial Toxins

Bacterial toxins are sophisticated virulence factors that enable pathogenic bacteria to interact with, invade, and damage host tissues. These toxins fall broadly into two types: protein exotoxins, which are secreted into the environment and target specific host receptors, and lipopolysaccharide endotoxins, which are structural components of the bacterial outer membrane released primarily during bacterial lysis or membrane shedding. Exotoxins generally act more selectively, binding to cell...
Determinants of Bacterial Pathogenicity and Virulence01:20

Determinants of Bacterial Pathogenicity and Virulence

Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...
Regulation of Bacterial Virulence01:28

Regulation of Bacterial Virulence

Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...
Diphtheria01:28

Diphtheria

Diphtheria is an acute, toxin-mediated infectious disease that primarily affects the upper respiratory tract. It is caused by Corynebacterium diphtheriae, a Gram-positive, pleomorphic rod that lacks spore-forming capability and exhibits a characteristic club-shaped morphology under microscopic examination. While C. diphtheriae can asymptomatically colonize mucosal surfaces, clinical disease manifests only when the bacterial strain is lysogenized by a specific β-corynephage. This phage...
Bacterial Gastroenteritis01:18

Bacterial Gastroenteritis

Bacterial gastroenteritis, characterized by diarrhea, abdominal cramps, and vomiting, is often caused by ingestion of contaminated food or water and is frequently associated with pathogenic Escherichia coli strains. These microbes exploit two principal mechanisms to inflict disease.Shiga toxin–producing E. coli, also referred to as STEC—notably O157:H7—release Shiga toxins that target ribosomes, blocking protein synthesis. The B subunit of the toxin binds the host glycolipid receptor...
Streptococcal Pharyngitis01:27

Streptococcal Pharyngitis

Streptococcal pharyngitis, commonly known as “strep throat,” is an acute infection of the oropharyngeal tissues caused by the Gram‑positive Group A Streptococcus (Streptococcus pyogenes). Transmission occurs primarily through respiratory droplets expelled during coughing, sneezing, or talking.Mechanisms of Host Entry and Immune EvasionUpon entering the host, S. pyogenes adheres to the mucosal epithelial cells of the pharynx via surface proteins, notably lipoteichoic acid and the antiphagocytic...