Related Experiment Video

Updated: Jul 14, 2026

A Visual Assay to Monitor T6SS-mediated Bacterial Competition
08:45

A Visual Assay to Monitor T6SS-mediated Bacterial Competition

Published on: March 20, 2013

Type VI secretion is a major virulence determinant in Burkholderia mallei

Mark A Schell1, Ricky L Ulrich, Wilson J Ribot

  • 1Department of Microbiology, University of Georgia, Athens, GA 30602, USA.

Molecular Microbiology
|June 9, 2007
PubMed

Insights

The VirAG system in Burkholderia mallei regulates virulence, with type VI secretion (T6S) genes being crucial. Overexpression of VirAG activates T6S genes, and mutations in these genes render the bacteria avirulent in hamsters.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Burkholderia mallei is a significant pathogen and biothreat agent.
  • The VirAG two-component system is essential for B. mallei virulence, but its regulated targets remain unidentified.

Purpose of the Study:

  • To identify virulence genes regulated by the VirAG system in Burkholderia mallei.
  • To elucidate the role of VirAG-controlled factors in bacterial virulence.

Main Methods:

  • Gene expression profiling using microarrays to assess transcriptional changes upon VirAG overexpression.
  • Genetic manipulation to create mutations in identified virulence gene clusters.
  • Biochemical assays including SDS-PAGE and mass spectrometry for protein secretion analysis.
  • Animal models (hamsters) to assess bacterial virulence and survival.

Main Results:

  • Overexpression of virAG led to the transcriptional activation of approximately 60 genes, including those involved in capsule production, actin-based motility, and type VI secretion (T6S).
  • Actin polymerization, while dependent on virAG and novel genes (bimB, bimC, bimE), was found to be dispensable for hamster virulence.
  • Genes encoding a T6S system were significantly upregulated (up to 30-fold), and mutations in this cluster resulted in complete avirulence in hamsters.
  • The T6S system secreted the Hcp-family protein BMAA0742, which was recognized by antibodies from infected hosts, indicating its in vivo production.

Conclusions:

  • The VirAG regulatory system controls key virulence factors in Burkholderia mallei, notably the type VI secretion system.
  • The type VI secretion system and its secreted effector BMAA0742 are critical for B. mallei virulence in a hamster model.
  • Actin motility is not essential for virulence, highlighting the primary role of T6S in host-pathogen interactions.

More Related Videos

Total Protein Extraction and 2-D Gel Electrophoresis Methods for Burkholderia Species08:31

Total Protein Extraction and 2-D Gel Electrophoresis Methods for Burkholderia Species

Published on: October 15, 2013

Transposon-insertion Sequencing as a Tool to Elucidate Bacterial Colonization Factors in a Burkholderia gladioli Symbiont of Lagria villosa Beetles09:55

Transposon-insertion Sequencing as a Tool to Elucidate Bacterial Colonization Factors in a Burkholderia gladioli Symbiont of Lagria villosa Beetles

Published on: August 12, 2021

Related Concept Videos

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...
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...
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):...
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...
Gene Regulation in Microbial Communities: Quorum Sensing01:28

Gene Regulation in Microbial Communities: Quorum Sensing

Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...
Inhalation Anthrax01:25

Inhalation Anthrax

Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive, spore-forming bacterium. It primarily affects herbivorous animals but can be transmitted to humans through skin contact, ingestion, or inhalation of spores.Cutaneous anthrax, the most common form, typically results from direct contact with bacterial spores through skin abrasions and is generally less severe. Gastrointestinal anthrax results from eating undercooked or contaminated meat. It affects the mouth, throat, or...