Scientists unravel one important secret of bacterial adaptation

Learning the secrets of how pathogenic bacteria manage to survive in the body of an animal or human may carry great implications for future development of new and better medical treatments.

Now, scientists at the University of Maryland School of Dentistry have unraveled one important secret of bacterial adaptation.

In a recently published paper in the prestigious Proceedings of the National Academy of Sciences (PNAS), researchers at the School's Department of Microbial Pathogenesis show how gram-negative bacteria regulate themselves to adapt to temperature changes. New methods to fight infections could result from their findings, says associate professor Robert Ernst, PhD, co-author of the paper.

Most gram-negative bacteria are considered pathogenic and are identified in a test by not retaining a violet color dye.

The paper, entitled "LPS remodeling is an evolved survival strategy for bacteria," describes the study conducted by lead researcher Yanyan Li, a visiting graduate student at the School of Dentistry who conducted research in Ernst's lab during a 2 ½ - year fellowship. She and a team of researchers studied the changes that occur on the surface of bacteria when the organism adapts to growth at different temperatures. Li is now at Jiangnan University in Wuxi, China.

All bacteria must adapt to survive when they enter a host. Alterations in the structure of the outer membrane surface of bacteria called LPS is one singular mechanism that is responsible for this surface adaptation, explains Ernst. "We knew that the surface of the bacteria changed when it enters a human or animal, but we didn't understand how."

To study bacterial adaptation, Li manipulated the temperature and analyzed how the bacterial surface changed. This analysis showed that at different temperatures, specific LPS structures were present in the outer membrane. She also identified that this adaptation required a second LPS enzyme acquired from a different species of bacteria. Li then mutated each of these bacterial enzymes, which prevented the bacteria from being able to adapt to warm-blooded human temperatures.

The altered bacterial strain was avirulent, which means that it did not kill its host, says Ernst.

Additionally, the altered strain protected the host from a subsequent lethal challenge.

Researchers could use these findings to generate a live vaccine strain, or identify bacterial components that could be the basis for future vaccines, Ernst says. "I find it rewarding to finally understand what allows this organism to adapt. Being able to analyze how bacteria alter their membranes could be valuable to studies in the future," he concludes.

The PNAS paper is titled, "LPS remodeling is an evolved survival strategy for bacteria."