"We are one of the few groups that are trying to understand the physical interactions with the environment that make spirochetes such successful pathogens," says senior author Dr. Charles Wolgemuth of the University of Arizona in Tucson. "We've previously understood very little about how these bacteria move through and into our organs, tissues, and central nervous system, but our work sheds light on these processes and could form the basis for novel therapeutics that target the bacterium's ability to invade."
Dr. Wolgemuth and his team, in collaboration with Dr. Justin Radolf at the University of Connecticut Health Center, found that the swimming speeds of the bacteria decrease with increases in the viscosity of their external environment, even though their motors—called flagella—are entirely intracellular. The team then used mathematical modeling to determine how these flagellar motors propel the undulating bacteria forward through viscous fluids. Finally, they fit their simulated data to their experimental data to reveal how external forces affect the movement of the Lyme disease and syphilis spirochetes.
The researchers also showed that both types of spirochetes (syphilis's Treponema pallidum
and Lyme disease's Borrelia burgdorferi
) respond to changes in viscosity in a similar manner and can be explained by the same biophysical model. "Since the syphilis bacterium cannot be cultured in the lab, our results show that data derived from studying the Lyme disease bacterium is highly informative about the syphilis bacterium and can be used as a 'surrogate' for it," says Dr. Wolgemuth.