““They worked with the same strain of timid mice that Collins studied, and managed to change the animals' behaviour by feeding them with a single strain of Lactobacillus rhamnosus - a bacterium commonly used in yoghurts and dairy products. After the mice ingested this strain, known as JB-1, they were better able to overcome anxiety: they spent more time in the exposed parts of a maze, or the centre of an open field. They were also better at resisting negative moods: when dropped into a bottle of water, they spent more time paddling away than floating aimlessly. These kinds of test are commonly used to test the effectiveness of psychiatric drugs, and JB-1 was behaving rather like substances with anti-anxiety and antidepressant properties. "It was like the mice were on low doses of Prozac or Valium," says Cryan.””