A  bacterial infection turns non-farming social amoebae into farmers, Washington University evolutionary biologists report in the Aug. 24 issue of Proceedings of the National Academy of Sciences.

Some social amoebae farm the bacteria they eat. Now a collaboration of scientists at Washington University in St. Louis and Harvard University has taken a closer look at one lineage, or clone, of  D. discoideum farmer. This farmer carries not one but two strains of bacteria. One strain is the “seed corn” for a crop of edible bacteria, and the other strain is a weapon that produces defensive chemicals. The edible bacteria, the scientists found, evolved from the toxic one.