I Contain Multitudes: Microbe Minute

To most animals, eucalyptus leaves are toxic if you eat enough of them. Yet koalas eat almost nothing else. Their secret? Microbes. The tannins in eucalyptus keep the leaves from being digested, but the koala's gut is packed with bacteria that unlock the nutrients.

Caffeine is one of the world’s most popular psychoactive drugs. Caffeine is made in coffee plants--and can act as a deterrent to insect predators but one beetle has found a countermeasure--microbes.

These tropical fish have a signature defense. But inside some is more protection--a potent toxin made by microbes. Those with spines have even more security; and there’s a third defense that some of these fish share. A neurotoxin on the skin and inner organs that’s produced by bacteria. It can be deadly to many creatures including humans. Oddly, some blowfish with this toxin are a delicacy.

After they lay their eggs, iguana mothers don't stick around to help their young. Hatchlings must seek out the adults' droppings, loaded with microbes that will help them break down plants. Teamwork plays a part too. Highly social, the iguanas huddle in pods, spreading bacteria from one to another. Sharing germs gives these babies a boost at this fragile time of life.