ISABEL GORDOBacteria exposed to antibiotics rapidly acquire mutations that allow them to develop resistance to the drugs, and this process is fairly well understood. Scientists have now looked at the evolution of bacterial resistance toward live agents: cells of the immune system. In a report published in PLOS Pathogens today (December 12), a team led by Isabel Gordo from the Instituto Gulbenkian de Ciência in Oeiras, Portugal, challenged the common human intestinal bacterium Escherichia coli with mouse macrophages—immune system cells that engulf foreign elements like bacteria—and observed the rapid evolution of mutants capable of escaping capture. The same E. coli mutants could successfully establish infections in mice.
“This work on the development of E. coli macrophage resistance and virulence is important,” wrote James Shapiro, a professor of microbiology at the University of Chicago who was not involved in the work, in an e-mail to The Scientist. “It documents how encounters with mammalian host defense cells can stimulate rapid adaptation in bacteria.”
Although the authors only tested for E. coli virulence for one month, some mutants emerged in as few as four days.
Bacteria have evolved several defences to avoid being internalized by macrophages—sticky outer coverings, formation of filaments and biofilms among them. The evolution of such defences has been studied previously, but not through an evolutionary experiment such as this one performed by Gordo’s team. “I would have thought that the answer ...
