Genetic tweak turned plague bacterium deadly
Mutation in newly acquired gene transformed Yersinia pestis into a mass killer
![Yersinia pestis bacteria](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2015/06/ss_plague_free.jpg?fit=860%2C460&ssl=1)
TINY KILLERS Acquiring one gene and one mutation allowed these plague bacteria, Yersinia pestis (shown in yellow in a flea’s digestive system in this colored scanning electron micrograph), to cause deadly pandemics.
NIAID