http://www.mysanantonio.com/news/metro/stories/MYSA041106.01B.mycoplasma.d4b8458.html
San Antonio scientist finds how bug hurts cells
Web Posted: 04/11/2006 12:00 AM CDT
Cindy Tumiel
Express-News Staff Writer
Scientists have long puzzled over how an oddly shaped bacterium called
mycoplasma pneumoniae is able to cause a wide variety of respiratory
illnesses, including pneumonia, bronchitis and asthma flare-ups.
Now, after three decades of work, San Antonio microbiologist Joel Baseman says
he has an answer: Once inside the body, the bug produces a toxin that injures
the delicate cells of the respiratory tract.
Experts are touting the discovery as a major breakthrough that could lead to the
development of vaccines, diagnostic tests and therapeutic medications.
"This is earthshaking," said Joseph Tully, retired chief mycoplasma investigator
at the National Institutes of Health. "It answers a lot of questions about a
whole battery of these things."
Mycoplasmas are a form of bacterium and the smallest organisms without cell
walls, which enables them to fuse with cells and disrupt their functions.
A number of mycoplasma species are known to cause diseases in humans and
aggravate chronic conditions. One form has been linked to pelvic diseases, and
another is suspected of contributing to the onset of illness in people with HIV
infections.
Mycoplasma pneumoniae is one of the most common respiratory disease agents. It
is the culprit in community-acquired pneumonia, a stubborn form of the illness
that spreads easily in communal living situations, such as military barracks and
jails. It also has been linked to other respiratory ailments such as asthma and
has been implicated in joint, liver and cardiac syndromes.
Scientists have struggled for years to understand how all mycoplasmas become
virulent.
"It's been baffling for all of us who have been working in this field, plus all
the people who work in infectious disease," said Baseman, chairman of
microbiology and immunology at the University of Texas Health Science Center.
Baseman said his team "went fishing," using an abundant lung protein to see what
molecule from the mycoplasma would grab the hook. The technique worked —
identifying a key protein in the mycoplasma that enabled the organism to attach
to the lung protein.
"We fished out one specific protein and it turned out to be this toxin," Baseman
said.
The toxic protein attacks in two ways, he said. It cuts a cell molecule called
NAD into two pieces and acts to damage the cell membrane. Both actions can kill
a cell, Baseman said.
The study was published Monday on the Web site of the journal Proceedings of the
National Academy of Sciences.
Understanding this chemical activity opens up a range of future studies, said
Dr. R. Doug Hardy, an assistant professor at the University of Texas
Southwestern Medical School in Dallas.
"By discovering this toxic protein, it is possible that we will be able to make
vaccines to protect people from it, which is very exciting," Hardy said. "We'll
also be able to develop better diagnostic tests to look for infections."
Tully, the retired mycoplasma investigator, said other scientists who study
mycoplasmas will now revisit their work to look for similar toxin production in
other species of the bug.
"Everybody is going to have to go back 20 years and look at all these other
organisms that we know can produce mild diseases in humans and whether that is
associated with a toxin," Tully said.
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ctumiel@express-news.net