The findings suggest that the protein, called BptA, is essential for the bacterium Borrelia burgdorfei (Bb) to survive in the gut of its tick host and may offer a potential new target for agents aimed at eradicating Lyme disease.

Results of the multisite study are currently online and will appear in an upcoming issue of the Proceedings of the National Academy of Sciences.

The bacterium that causes Lyme disease lives in infected mammals and in the midgut of ticks. When an infected tick bites an animal or a human, the bacteria are transmitted to the new host. Infection causes fever, malaise, fatigue, headache, muscle and joint aches, and a characteristic "bull's-eye" rash that surrounds the site of infection.

In the study, researchers genetically altered the Bb bacterium to make a "knockout" form that lacked a gene that codes for the protein BptA. Without the protein, bacteria were unable to utilize the blood on which the tick feeds when it bites a victim.

"As far as we can tell, Bb bacteria normally utilize blood as their main nutrient source, just as the tick does," said Dr. Michael Norgard, chairman of microbiology at UT Southwestern and senior author of the study. "When the tick is not feeding, and no nutrients are coming in, the bacteria are sort of in a quiescent state, waiting in the tick's midgut, which is equivalent to our digestive system."

When blood enters the tick gut, Dr. Norgard said it appears that changes in temperature and acidity signal the bacteria that the nutrient is present, triggering the bacteria to replicate in large numbers and migrate to the tick's salivary glands, where they are transmit
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Contact: Amanda Siegfried
amanda.siegfried@utsouthwestern.edu
214-648-3404
UT Southwestern Medical Center
25-Apr-2005