New way to learn about, potentially block traits in harmful pathogens

These are electron micrographs of Chlamydia mutant inside a of a cell. These particular mutant bacteria, colored red, are defective in secreting high levels of virulence proteins, seen here as the accumulating dark granules in between two bacterial membranes. Credit: Bidong Ngyuen, Duke Molecular Genetics and Microbiology

Researchers at Duke University Medical Center have developed a new way to identify the genes of harmful microbes, particularly those that have been difficult to study in the laboratory.

This new method uses chemicals to create , followed by genomic sequencing to identify all mutations. By looking for common genes that were mutated in Chlamydia sharing a particular trait, the investigators were able to rapidly "zero in" on the genes responsible for that trait.

The approach is versatile and inexpensive enough that it could be applied to study a range of , said Raphael Valdivia, Ph.D., an associate professor of and microbiology at Duke.

"We were able to learn about genes that allow Chlamydia to flourish in their hosts without the traditional, lengthy process of domesticating the pathogen to accept recombinant DNA," Valdivia said. "Our approach marries classical microbiology techniques with 21st century genome-sequencing technologies. If you encounter a new dangerous microorganism and want to determine what genes are important, I think this represents an effective way to learn all we can, as fast as we can."

One of the goals in studying microbial pathogens that harm humans and animals is to locate and disrupt the genes required for infection, Valdivia said.

The microbe in this study, Chlamydia, is usually sexually transmitted, hides in , and is a type of bacteria that must cause disease to be transmitted from one host to another. Chlamydia is the leading sexually transmitted infection and a risk factor for and infertility.

Prior to this work, the function of many Chlamydia genes had to be inferred by their similarity to genes from other bacteria. "By isolating mutants that don't grow well inside cells and identifying the underlying mutations, we can learn a lot about how these genes contribute to disease," Valdivia said. "These are the activities we'd like to block."

"For us, this significantly accelerates the analysis of Chlamydia and importantly, should be applicable to many other microbes that have been difficult manipulate with recombinant DNA approaches," he said. Valdivia suggested that even associated with our normal intestinal flora, which are notoriously difficult to manipulate, are now open to exploration so that we can learn how their genes influence human health, including dietary disorders and inflammatory bowel disease.

The work was published on Jan. 9 in the early edition of the Proceedings of the National Academy of Sciences.

Valdivia also said that the new technique could help to create vaccines that have a combination of mutations that affect the pathogen's virulence. "That way we can cripple some aspects of the bacterium's ability to thrive intact in a host, while still allowing the bacterium to replicate enough to prime the immune system against it."

Related Stories

Newly designed molecule blocks chlamydia bacteria

Jul 20, 2011

Researchers at Duke University Medical Center have discovered a way to block the damaging actions of Chlamydia, the bacteria responsible for the largest number of sexually transmitted infections in the United States.

Chlamydia utilizes Trojan horse tactics to infect cells

Oct 06, 2011

A novel mechanism has been identified in which Chlamydia trachomatis tricks host cells into taking up the bacteria. Researchers from University of California San Francisco, led by Joanne Engel, report their findings in the ...

New Chlamydia test shows type of infection

May 24, 2011

A new Chlamydia test can quickly and easily demonstrate the subtype (serovar) of the bacterium Chlamydia trachomatis a person is infected with. This has important clinical implications, because some Chlamydia subtypes, that ...

Recommended for you

Where Ebola battles are won

2 hours ago

(HealthDay)—Four hospitals that are home to advanced biocontainment facilities have become America's ground zero in the treatment of Ebola patients.

Depression tied to worse lumbar spine surgery outcomes

5 hours ago

(HealthDay)—Depressive symptoms are associated with poorer long-term outcome in patients undergoing surgery for lumbar spinal stenosis (LSS), according to research published in the Oct. 1 issue of The Sp ...

Ebola death toll edging to 4,900 mark: WHO

5 hours ago

The death toll in the world's worst-ever Ebola outbreak has edged closer to 4,900, while almost 10,000 people have now been infected, new figures from the World Health Organization showed Wednesday.

US to track everyone coming from Ebola nations

6 hours ago

U.S. authorities said Wednesday that everyone traveling into the U.S. from Ebola-stricken nations will be monitored for symptoms for 21 days. That includes returning American aid workers, federal health employees ...

User comments