Helicobacter pylori, a globally distributed gastric bacterium, is genetically highly adaptable. Microbiologists at LMU have now characterized its population structure in individual patients, demonstrating an important role of antibiotics for its within-patient evolution.
Researchers led by microbiologist Sebastian Suerbaum (Chair of Medical Microbiology and Hospital Epidemiology at LMU's Max von Pettenkofer Institute have now examined the genetic diversity of the species in the stomachs of 16 patients, and identified specific adaptations that enable the bacterium to colonize particular regions of the stomach.
At the initial sample from this individual, the H. pylori population was highly diverse and showed no signs of resistance to any of the antibiotics tested during growth in the laboratory.
However, in a sample collected 2 years later, the level of diversity within the population was extremely low, and the bacteria had become completely resistant to a frontline antibiotic.
Over the course of the intervening 2 years, the population had apparently undergone a massive reduction in size, which set the scene for the subsequent large-scale change in the structure of the surviving population.”
The article tells about the evolutionary dynamics of the species. However, the species stays the same throughout history, although another site says it is said to have “evolved over the millennia since its migration out of Africa along with its human host approximately 60,000 years ago.”
This is counter to all Darwinian expectations of how a H. pylori population should grow. It stays the same after millions of years, but antibiotics kill it off.
Ludwig Maximilian University of Munich. 2019, Signs of selection in the stomach. Phys.org. (24 May).