Mutation makes bubonic plague more lethal

CHICAGO, May 5 (UPI) -- U.S. scientists say bubonic plague bacteria might be more virulent than other illness-causing bacteria because of a genetic mutation.

"The plague bacterium Yersinia pestis needs calcium in order to grow at body temperature," said University of Chicago Professor Robert Brubaker. "When there is no calcium available, it produces a large amount of an amino acid called aspartic acid. We found this is because Y. pestis is missing an important enzyme."

Bubonic plague has killed more than 200 million people and is the most devastating acute infectious disease known. Despite that, scientists say they are still uncertain about the molecular basis of its extraordinary virulence.

"Y. pestis evolved from its ancestor Y. pseudotuberculosis within the last 20,000 years, suggesting its high lethality reflects only a few genetic changes," Brubaker said. "We discovered that a single mutation in the genome of Y. pestis means the enzyme aspartase is not produced.

"This suggests that the absence of aspartase may contribute to serious disease," he said.

The research appears in the journal Microbiology.