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.

Cats are cunning, stealthy hunters and for prey like rodents, the smell of a feline means stay away. But we see a rat heading straight toward danger.  It's been tricked by a microbe.

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.

Microbes are the key to snow. When liquid water turns to ice, crystals sometimes need a place to start growing. Without that seed, water can cool to minus 40 degrees before freezing. Often, a bacterium acts as the seed. Bacteria are all around us, even swept up into the clouds by winds. There, they help ice crystals to form.

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.

The Eurasian hoopoe have a difficult road to adulthood. But they have protection from bacteria; a gland on the mother secretes a bacteria laden-paste that the mother smears on her eggs. These microbes help to defend the egg and chick against disease. The foul smelling paste may even drive away predators. So this bacterial partnership protects the hoopoe against threats, both big and small.

A grain weevil spends its early days nestled inside a cereal seed, but after it emerges into the world as an adult, the insect is in dire need of defenses. That credit goes to a microbial partner living inside the weevil’s gut, who produces the perfect chemicals to help build a sturdy, external skeleton.

Inside the gut of a locust is a powerful bacterial symbiont: a microbe that holds the key to coordinating the monstrous insect swarm. When the time is right, the microbe releases a chemical to help cue their insect host to take flight and head to greener pastures.