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By Root 1247 0

If I had microscopes for eyes, I could have watched the hundreds of E. coli Morales had given me as they wandered, fed, and grew. Each one is shaped like a microscopic submarine, enshrouded by fatty, sugary membranes. It trails propeller-like tails that spin hundreds of times a second. It is packed with tens of millions of molecules, jostling and cooperating to make the microbe grow. Once it grows long enough, it splits cleanly in two. Splitting again and again, it gives rise to a miniature dynasty. When these dynasties grow large enough, they become visible as golden spots. And together the spots reveal the path of Morales’s living signature.

E. coli may seem like an odd choice as a guide to life if the only place you’ve heard about it is in news reports of food poisoning. There are certainly some deadly strains in its ranks. But most E. coli are harmless. Billions of them live peacefully in my intestines, billions more in yours, and many others in just about every warm-blooded animal on Earth. All told, there are around 100 billion billion E. coli on Earth. They live in rivers and lakes, forests and backyards. And they also live in thousands of laboratories, nurtured in yeasty flasks and smeared across petri dishes.

In the early twentieth century, scientists began to study harmless strains of E. coli to understand the nature of life. Some of them marched to Stockholm in the late 1900s to pick up Nobel Prizes for their work. Later generations of scientists probed even further into E. coli’s existence, carefully studying most of its 4,000-odd genes and discovering more rules to life. In E. coli, we can begin to see how genes must work together to sustain life, how life can defy the universe’s penchant for disorder and chaos. As a single-celled microbe, E. coli may not seem to have much in common with a complicated species like our own. But scientists keep finding more parallels between its life and ours. Like us, E. coli must live alongside other members of its species, in cooperation, conflict, and conversation. And like us, E. coli is the product of evolution. Scientists can now observe E. coli as it evolves, mutation by mutation. And in E. coli, scientists can see an ancient history we also share, a history that includes the origin of complex features in cells, the common ancestor of all living things, a world before DNA. E. coli can not only tell us about our own deep history but can also reveal things about the evolutionary pressures that shape some of the most important features of our existence today, from altruism to death.

Through E. coli we can see the history of life, and we can see its future as well. In the 1970s, scientists first began to engineer living things, and the things they chose were E. coli. Today they are manipulating E. coli in even more drastic ways, stretching the boundaries of what we call life. With the knowledge gained from E. coli, genetic engineers now transform corn, pigs, and fish. It may not be long before they set to work on humans. E. coli led the way.

I hold the petri dish up to the window. I can see the trees and flowers through its agar gauze. Each spot of the golden signature refracts their image. I look at life through a lens made of E. coli.

Two

E. COLI AND THE ELEPHANT

“LUXURIOUS GROWTH”

ESCHERICHIA COLI HAS LURKED WITHIN our ancestors for millions of years, before our ancestors were even human. It was not until 1885 that our species was formally introduced to its lodger. A German pediatrician named Theodor Escherich was isolating bacteria from the diapers of healthy babies when he noticed a rod-shaped microbe that could produce, in his words, a “massive, luxurious growth.” It thrived on all manner of food—milk, potatoes, blood.

Working at the dawn of modern biology, Escherich could say little more about his new microbe. What took place within E. coli—the transformation of milk, potatoes, or blood into living matter—was mostly a mystery in the 1880s. Organisms were like biological furnaces, scientists agreed, burning food as fuel and creating heat, waste,