Hacking bacteria to fight cancer

In 1884, an unlucky patient who had a rapidly growing cancer in his neck came down with an unrelated bacterial skin infection. As he recovered from the infection, the cancer surprisingly began to recede. The infection had stimulated the patient's immune system. Today, synthetic biologists program bacteria to safely deliver drugs directly to tumors. How is this possible? Tal Danino investigates. [Directed by Chris Bishop, narrated by Addison Anderson].