JUL 08, 2016 10:41 AM PDT

Pathogenic Bacterium Uses Gene Amplification to Cause Infection

WRITTEN BY: Carmen Leitch
While most bacteria is harmless, some have evolved into pathogens, which have various ways of causing infectious disease. Investigators at Umeå University in Sweden have now discovered that some bacteria are able to multiply specific genes which are required for causing infection, thus inducing disease. 
Illustration of the discovery by Umeå researchers. To the left: inactive Yersinia bacteria with just one ring-shaped DNA strand cannot cause infection. To the right: active Yersinia bacteria with multiple DNA plasmids which can cause intestinal disease in the mouse. / Credit: Kemal Avican, Umeå University
Over 22 years ago, researchers at Umeå were the first to determine the infection strategy of Yersinia bacteria, a human pathogen which has a protein structure in the cell walls that resembles a syringe. The structure, called "Type III secretion system" or T3SS, enables the transfer of bacterial proteins into a host cell, destroying its metabolism. 

After that discovery, scientists have found T3SS in other species of bacteria, proving T3SS to be a common mechanism of infection mechanism that pathogens, such as a virus or virulent bacterium, use to destroy host cells. Umeå researchers have now found the link between disease and rapid production of the proteins required to form the so-called poisonous syringe. An overview of the T3SS mode of action is shown in the video below from Garland Science.
In collaboration with researchers at the Helmholtz Centre for Infection Research in Braunschweig, Germany, the team investigated the infection strategy of Yersinia pseudotuberculosis. Closely related to the deadly plague bacterium, this microbe can cause acute diarrhea, stomach pains and vomiting and stomach pains. The genes the bacteria need for infection are located on a circular extra chromosome, called a virulence plasmid.

 First, the investigators studied infected human cells in culture, then confirmed the findings with animal models. They learned that a lone copy of the virulence plasmid could not induce infection, but when the Yersinia bacteria came in contact with host cells, a "copying machine" was triggered, increasing the number of plasmids. So, for the first time researchers have shown that an increased amount of plasmid-encoded genes is required for the establishment of infection by pathogenic bacteria.

"Yersinia has developed a very clever strategy," says postdoctoral fellow Helen Wang and first author of the study that reported their findings in Science. "To carry a great number of plasmids, the bacteria need a lot of energy and it negatively affects the bacteria's metabolism and growth. But having one copy of the plasmid as a blueprint that can be rapidly amplified in case of infection is a very clever solution. Many copies of the plasmids give bacteria the opportunity to build up many T3SS and all the proteins needed to quickly knock out host cells during an infection," explains Wang.

"Our study represents a breakthrough in which we show that gene-dosage of plasmid-encoded genes is a fast regulatory strategy used by bacteria. This discovery will contribute to increased insights into bacterial resistance to antibiotics, and is a major step forward in our understanding of how bacteria cause disease," says Research Engineer Tomas Edgren, who led the study along with Professor Hans Wolf-Watz.

Sources: AAAS/Eurekalert!, Garland Science, Science
About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
AUG 09, 2018
Cell & Molecular Biology
AUG 09, 2018
Observing Development at the Cellular Level
A new method can track the formation and movement of lipids, DNA and proteins in live cells....
AUG 20, 2018
Genetics & Genomics
AUG 20, 2018
Using Population Genetics to Predict Disease Risk
Using genetics, this work has created a way to identify people at higher risk for five common diseases - before they show any symptom....
SEP 18, 2018
Cell & Molecular Biology
SEP 18, 2018
Visualizing the Organization of Human Cells With Machine Learning
Instead of fluorescent labeling, scientists found a way to use computers to identify cellular structures....
OCT 02, 2018
Cell & Molecular Biology
OCT 02, 2018
Approved Drug may Slow the Progression of Alzheimer's
For many, Alzheimer's disease is just a fact of old age; around 50 percent of people that live to age 85 will get the disorder....
OCT 02, 2018
Drug Discovery
OCT 02, 2018
Mycobacterial Lung Disease, FDA Approves New Drug
New drug seeking to treat antibiotic-resistant lung disease has just been approved by the U.S. Food and Drug Administration. The drug is called ‘Arik...
OCT 06, 2018
Cell & Molecular Biology
OCT 06, 2018
Risks Posed by the Keto Diet
It seems there is no shortage of diet trends, although we've moved on from Atkins and South Beach and into the world of Paleo and keto....
Loading Comments...