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Related Concept Videos

Defense Against Bacterial Pathogens01:31

Defense Against Bacterial Pathogens

The human immune system is a complex network of cells, tissues, and organs that work together to defend the body against bacterial infections. It consists of various immune cells, each playing a specific role in the defense mechanism.
Phagocytes
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Atypical Pneumonia

Atypical pneumonia, often caused by Mycoplasma pneumoniae, is a form of pulmonary infection that differs from the classical presentation of bacterial pneumonia in both its cause and clinical symptoms. Mycoplasma pneumoniae is a pleomorphic bacterium notable for its lack of a rigid cell wall. This structural characteristic imparts resistance to beta-lactam antibiotics and significantly influences the bacterium’s behavior within the human host.Other pathogens responsible for the disease include...
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Autophagy

Autophagy is a self-digesting process by which a cell protects itself from threats both within and outside the cell, ranging from abnormal proteins to invading bacteria. In this process, obsolete components of the cell and invading microbes are degraded by hydrolytic enzymes active in an acidic environment of the lysosomal lumen.
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Pneumonia is an infection of the lower respiratory tract that leads to inflammation of the lung parenchyma, often resulting in the accumulation of inflammatory exudate in the alveoli and airways. Unlike the watery, low-protein fluid exudate in pulmonary edema, the exudate in this case is a thick fluid rich in immune cells, proteins, and debris produced during infection and inflammation.This impairs gas exchange and can lead to consolidation of lung tissue. The infection may be caused by a...

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Related Experiment Video

Updated: Jun 19, 2026

Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins
06:05

Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins

Published on: September 30, 2014

THE AUTOLYTIC SYSTEM OF PNEUMOCOCCI.

R J Dubos1

  • 1Hospital of The Rockefeller Institute for Medical Research.

The Journal of Experimental Medicine
|October 30, 2009
PubMed
Summary

Living pneumococcus cells possess a bacteriolytic system that can lyse heat-killed bacteria. This enzyme system can also alter Gram staining and release sugars, suggesting a dual function in bacterial cell wall degradation.

Area of Science:

  • Microbiology
  • Enzymology
  • Bacterial Cell Wall Structure

Background:

  • Living Streptococcus pneumoniae cells possess a bacteriolytic system.
  • This system can lyse heat-killed pneumococci, affecting Gram staining, cell morphology, and suspension clarity.

Purpose of the Study:

  • To investigate the bacteriolytic system of Streptococcus pneumoniae.
  • To characterize the enzyme responsible for altering Gram staining and cell lysis.
  • To explore the substrate specificity of the identified enzyme.

Main Methods:

  • Treatment of heat-killed pneumococci with the bacteriolytic complex.
  • Partial purification and characterization of the responsible enzyme.
  • Assays for enzyme activity on bacterial cell structures and specific glycosides.

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Last Updated: Jun 19, 2026

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06:05

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Main Results:

  • The bacteriolytic system causes lysis, Gram-negative conversion, and suspension clearing in heat-killed pneumococci.
  • Under specific conditions, pneumococci can be rendered Gram-negative without significant morphological change or clearing.
  • The enzyme responsible for Gram-negative conversion is resistant to proteolytic enzymes and retains activity on a significantly degraded cell structure.
  • The same enzyme preparation liberates reducing sugars from acetyl amino glucose glucuronides.

Conclusions:

  • A bacteriolytic system in living pneumococci can degrade heat-killed cells.
  • A specific enzyme within this system can alter Gram staining properties and lyse pneumococci.
  • This enzyme exhibits dual activity, affecting both bacterial cell walls and specific glycosidic linkages, suggesting a broader role in microbial degradation.