I Contain Multitudes: The Microbes Within Us and a Grander View of Life

by Ed Yong

there are more bacteria in your gut than there are stars in our galaxy.

“Animals might be evolution’s icing, but bacteria are really the cake.”

Then, on one fateful occasion, a bacterium somehow merged with an archaeon, losing its free-living existence and becoming entrapped forever within its new host. That is how many scientists believe eukaryotes came to

chassis of the eukaryotic cell while the bacterium eventually transformed into the mitochondria.

“black hole at the heart of biology”. There’s a huge void between the simpler cells of bacteria and archaea and the more complex ones of eukaryotes,

The latest estimates suggest that we have around 30 trillion human cells and 39 trillion microbial ones – a roughly even split.

There are fewer than 100 species of bacteria that cause infectious diseases in humans;8 by contrast, the thousands of species in our guts are mostly harmless.

At worst, they are passengers or hitchhikers. At best, they are invaluable parts of our bodies: not takers of life but its guardians. They behave like a hidden organ, as important as a stomach or an eye but made of trillions of swarming individual cells rather than a single unified mass.

Your cells carry between 20,000 and 25,000 genes, but it is estimated that the microbes inside you wield around 500 times more.9

combined with their rapid evolution, makes them virtuosos of biochemistry,