Related Experiment Video

Updated: May 9, 2026

Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization
10:13

Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization

Published on: August 11, 2018

Distinct localization of the complement C5b-9 complex on Gram-positive bacteria

Evelien T M Berends1, Johanna F Dekkers, Reindert Nijland

  • 1Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, the Netherlands.

Cellular Microbiology
|July 23, 2013
PubMed

Insights

Complement activation on Gram-positive bacteria leads to specific Membrane Attack Complex (MAC) deposition. This previously unrecognized interaction occurs at specialized bacterial regions, challenging existing models of MAC assembly and function.

Area of Science:

  • Immunology
  • Microbiology
  • Molecular Biology

Background:

  • The complement system's Membrane Attack Complex (MAC or C5b-9) is crucial for immune defense, directly killing bacteria.
  • Gram-positive bacteria possess a thick peptidoglycan layer that typically protects them from MAC-mediated lysis.
  • Some Gram-positive pathogens secrete proteins that inhibit MAC formation, adding complexity to this interaction.

Purpose of the Study:

  • To investigate the deposition patterns of the Membrane Attack Complex (MAC or C5b-9) on Gram-positive bacterial surfaces.
  • To understand the implications of MAC deposition on Gram-positive bacteria, particularly in light of their known resistance mechanisms.
  • To explore potential new models for MAC assembly and function based on observed interactions.

Main Methods:

  • Complement activation was induced on Gram-positive bacteria using serum.
  • Immunoblotting was employed to detect and characterize C9 in both monomeric and polymeric forms, indicating C5b-9 complex formation.
  • Confocal microscopy was utilized to visualize the spatial distribution of C5b-9 deposition on bacterial cells.

Main Results:

  • Complement activation resulted in specific surface deposition of C5b-9 complexes on Gram-positive bacteria.
  • SDS-stable C9 polymers confirmed the presence of ring-structured C5b-9 complexes.
  • Confocal microscopy revealed non-random C5b-9 deposition at specialized regions: the division septum in Streptococcus pyogenes and the poles in Bacillus subtilis.
  • C5b-9 deposition patterns contrasted with the random surface distribution of C3b.

Conclusions:

  • A previously unrecognized interaction between the C5b-9 complex and Gram-positive bacteria was identified.
  • MAC deposition on Gram-positive bacteria occurs at specific cellular locations, not randomly.
  • These findings suggest a potential need for revised models of MAC assembly and function in the context of Gram-positive pathogens.

More Related Videos

High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer's Disease Gene Susceptibility Assessment07:26

High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer's Disease Gene Susceptibility Assessment

Published on: July 18, 2017

Separation of the Cell Envelope for Gram-negative Bacteria into Inner and Outer Membrane Fractions with Technical Adjustments for Acinetobacter baumannii10:24

Separation of the Cell Envelope for Gram-negative Bacteria into Inner and Outer Membrane Fractions with Technical Adjustments for Acinetobacter baumannii

Published on: April 10, 2020

Related Concept Videos

Complement System01:27

Complement System

The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a membrane...
Formation of Lipopolysaccharides01:19

Formation of Lipopolysaccharides

Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin, triggering...
Antibody Actions01:26

Antibody Actions

Antibodies, or immunoglobulins, are critical players in the immune system's arsenal against invading pathogens. Produced by B cells and plasma cells, their primary role is to detect and bind to specific antigens, molecules found on the surface of pathogens like bacteria or viruses. Beyond antigen recognition, antibodies perform several vital functions that contribute to immune defense.
Neutralization
Antibodies can bind to pathogens, preventing them from infecting host cells. This process...
Special Staining Techniques01:13

Special Staining Techniques

Specialized staining techniques play a vital role in microbiology by enabling the visualization of specific bacterial structures that remain undetectable with standard microscopy methods. These techniques not only enhance the structural visualization of bacterial cells but also provide critical insights into their pathogenicity and classification. Additionally, they support diagnostic and research endeavors in microbiology by identifying key bacterial features.Capsule Staining for Virulence...
Bacterial Cell Wall01:22

Bacterial Cell Wall

The bacterial cell wall is an essential structural component that encases the plasma membrane, preserving cellular integrity, determining shape, and protecting against osmotic stress. This rigid yet flexible structure primarily comprises peptidoglycan, a polymer that forms a mesh-like matrix conferring mechanical strength and flexibility.Peptidoglycan Composition and StructurePeptidoglycan, the core of the bacterial cell wall, comprises alternating units of N-acetylglucosamine (NAG) and...
Differential Staining Technique01:26

Differential Staining Technique

Differential staining is an essential microbiological technique that exploits variations in cell wall structures to classify and identify microorganisms. It facilitates the distinction of bacteria, aiding in diagnostic and research applications. Two of the most widely used differential staining methods are Gram staining and acid-fast staining, both of which rely on the chemical and structural differences in bacterial cell walls.Gram Staining TechniqueGram staining differentiates bacteria by...