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Chlamydia Genome Sequenced for First Time, Says Campus Researcher

by Kathleen Scalise, Public Affairs
posted November 18, 1998

Public Health Professor Richard Stephens and colleagues reported in Science last month the first complete sequencing of the Chlamydia trachomatis genome.

This bacteria infects humans and causes both chlamydial genital tract infections, which are sexually transmitted, and trachoma, a leading cause of preventable blindness, said Stephens, lead author on the Oct. 23 Science paper.

Sequencing of the Chlamydia genome revealed a wealth of knowledge about the poorly understood organism, he said.

"We know more about Chlamydia from this one study than we knew before from 40 years of research," Stephens said. "We found new targets on the surface that could help us develop a vaccine and we found new proteins that interact with the host and could help us with diagnostics."

While trachoma is more common in other parts of the world, chlamydial genital tract infections are the most commonly reported disease of any kind in the U.S., Stephens said.

Trachoma is most often contracted in the U.S. by teens between the ages of 14 and 19. Though the disease is prevalent in both sexes, women suffer its most serious effects, including "chronic pelvic pain, ectopic pregnancy and involuntary sterilization," said Stephens.

Stephens said finding better ways to diagnose this disease, which the new findings could make possible, is important since such infections often show no symptoms before permanent damage occurs.

"From 60 to 70 percent of new chlamydial infections go undiagnosed in young women," he said. "It is a very significant disease agent in teenage girls."

Stephens said what was learned about how this organism operates "is just tremendous," he said. "I think for the scientific community studying Chlamydia, it's a huge advance."

Chlamydia trachomatis, as well as its variants in other species, is an unusual organism since it is not closely related, or phylogenetically similar, to other families of bacteria, Stephens said. It probably diverged from the rest long ago and has evolved along different lines.

"These are pathogens that have been in humans a long time," Stephens said.

Not much was previously known about the complex biology of C. trachomatis in part because it "only grows in human cells," said Stephens. "We had no methods of doing genetics with this organism."

But now, Stephens and the other researchers on the project have sequenced the more than one million base pairs in Chlamydia trachomatis' genome.

Besides Stephens, other researchers on the project included staff scientist Claudia Lammel and graduate student Wayne Mitchell of Berkeley's Program in Infectious Disease; and colleagues from the DNA Sequencing and Technology Center at Stanford University; the National Center for Biotechnology Information at the National Library of Medicine, National Institutes of Health; and the Francis I. Proctor Foundation at UC San Francisco.

Their research was funded by the Sexually Transmitted Disease Branch of the National Institute for Allergy and Infectious Diseases.


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