Dec. 12, 2013 — Bacteria can evolve rapidly to adapt to environmental change. When the "environment" is the immune response of an infected host, this evolution can turn harmless bacteria into life- threatening pathogens. A study published on December 12 in PLOS Pathogens provides insight into how this happens.
Isabel Gordo and colleagues from the Instituto Gulbenkian de Ciencia in Oeira, Portugal, have for the first time devised an experimental system to observe and study the evolution of bacteria in response to encounters with cells of the mammalian immuney system. They found that in less than 500 bacterial generations (or 30 days),
the bacteria became more resistant to being killed by immune
cells and acquired the ability to cause disease in mice.
"Escherichia coli bacteria show an extraordinary amount of diversity:
Many are benign commensal bacteria, but some are deadly pathogens," says Isabel Gordo. "It is thought that many strains of E. coli that cause disease in humans evolved from commensal strains. We thought that experimental evolution would be a powerful tool to directly observe some of the steps E. coli may take in the transition from commensalism to pathogenesis." http://www.sciencedaily.com/releases/2013/12/131212185831.htm