Related Experiment Video

Updated: Nov 2, 2025

Using Fluorescent Proteins to Visualize and Quantitate Chlamydia Vacuole Growth Dynamics in Living Cells
07:42

Using Fluorescent Proteins to Visualize and Quantitate Chlamydia Vacuole Growth Dynamics in Living Cells

Published on: October 13, 2015

7.7K

A Chlamydial Plasmid-Dependent Secretion System for the Delivery of Virulence Factors to the Host Cytosol

Lei Lei1, Chunfu Yang1, Michael John Patton1

  • 1Chlamydial Diseases Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.

Mbio
|June 8, 2021
PubMed

Insights

Chlamydia bacteria use a novel plasmid-dependent system to secrete virulence factors. This system involves unique globular structures that export key proteins from the inclusion to the host cell cytosol.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Cell Biology

Background:

  • Chlamydia are obligate intracellular bacteria with a unique developmental cycle.
  • The chlamydial plasmid is crucial for virulence, regulating key factors like Pgp3 and GlgA.
  • The mechanism for secreting these factors from the inclusion to the host cytosol was previously unknown.

Purpose of the Study:

  • To identify and characterize the novel secretion system responsible for delivering chlamydial virulence factors to the host cytosol.
  • To elucidate the role of plasmid gene protein 4 (Pgp4) in this secretion process.

Main Methods:

  • Identification of globular structures originating from reticulate bodies.
  • Analysis of protein content within these structures, including Pgp4-regulated proteins.
  • Genetic manipulation to assess the necessity of Pgp4 for structure formation and secretion.
  • Comparison with known type 2 and type 3 secretion systems.
  • Characterization of globular structures using markers like lipopolysaccharide, outer membrane protein, and heat shock protein 60.

Main Results:

  • A novel plasmid-dependent secretion system was identified, utilizing distinct globular structures.
  • These structures, originating from midcycle reticulate bodies, contain virulence factors Pgp3 and GlgA, along with Pgp4-regulated proteins.
  • Pgp4 is essential for the formation of these globular structures and the subsequent secretion of Pgp3 and GlgA.
  • Secretion via these structures is independent of known chlamydial secretion systems (T2SS and T3SS).
  • Globular structures resemble outer membrane vesicles, enriched in lipopolysaccharide.

Conclusions:

  • A novel Pgp4-dependent secretion system, mediated by outer membrane vesicles, transports chlamydial virulence factors to the host cytosol.
  • This discovery provides a new understanding of Chlamydia pathogenesis and immune evasion strategies.
  • The identified system is critical for exporting plasmid-regulated virulence factors, impacting host-pathogen interactions.
Keywords:
Chlamydiaplasmidsecretionvirulence factors

More Related Videos

Markerless Gene Deletion by Floxed Cassette Allelic Exchange Mutagenesis in Chlamydia trachomatis10:35

Markerless Gene Deletion by Floxed Cassette Allelic Exchange Mutagenesis in Chlamydia trachomatis

Published on: January 30, 2020

6.9K
Forward Genetic Approaches in Chlamydia trachomatis09:03

Forward Genetic Approaches in Chlamydia trachomatis

Published on: October 23, 2013

13.0K

Related Concept Videos

Bacterial Phylum Chlamydiae01:29

Bacterial Phylum Chlamydiae

The phylum Chlamydiae or Chlamydiota is composed of a single order, Chlamydiales. This phylum consists entirely of obligate intracellular parasites that infect eukaryotic hosts. While human pathogens within this group have been studied extensively, the phylum encompasses many species capable of interacting with various eukaryotic organisms. Members of Chlamydiae are typically small cocci, approximately 0.5 μm in diameter, and exhibit a distinctive developmental cycle. As is characteristic...
195
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):...
293
Plasmids01:28

Plasmids

Plasmids are extrachromosomal DNA molecules found in bacteria, archaea, and some eukaryotic microbes like yeast. These small, circular DNA structures typically contain fewer than 30 genes, although some may exist linearly. Plasmids vary in their number within a cell, known as copy number. Single-copy plasmids are present in one copy per cell and multi-copy plasmids are present in multiple copies, reaching over 100 copies per cell.Plasmids usually replicate independently of the chromosomal DNA...
457
Bacterial Translocation and Protein Secretion01:26

Bacterial Translocation and Protein Secretion

Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...
199
Mechanism of Conjugation01:19

Mechanism of Conjugation

Bacterial conjugation is a mechanism of horizontal gene transfer that enables the exchange of genetic material between bacterial cells through direct contact. This process is facilitated by a donor cell carrying a conjugative plasmid, which encodes genes necessary for pilus formation, DNA replication, and transfer. The conjugative plasmid plays a central role in initiating and executing the transfer of genetic material.The tra region of the conjugative plasmid encodes proteins responsible for...
332
Viral Replication: Lytic Cycle01:20

Viral Replication: Lytic Cycle

Bacteriophages, or phages, are viruses that specifically infect bacteria. Among them, T-even bacteriophages, such as T4, exhibit a well-characterized lytic replication cycle in Escherichia coli (E. coli). This process ensures the rapid proliferation of the virus while ultimately leading to the destruction of the bacterial host.Attachment and DNA InjectionThe infection process begins with the recognition and binding of the T4 phage to the E. coli cell surface. Tail fibers of the phage...
599