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. And together the spots reveal the path of Morales's living signature.Į. When these dynasties grow large enough, they become visible as golden spots. Splitting again and again, it gives rise to a miniature dynasty. Once it grows long enough, it splits cleanly in two. It is packed with tens of millions of molecules, jostling and cooperating to make the microbe grow. It trails propeller-like tails that spin hundreds of times a second. Each one is shaped like a microscopic submarine, enshrouded by fatty, sugary membranes. coli Morales had given me as they wandered, fed, and grew. If I had microscopes for eyes, I could have watched the hundreds of E. Oxygen molecules disappeared from the air in the dish, and carbon dioxide and beads of water were created. Old molecules snapped apart and were forged together into new ones. The lifeless agar in my petri dish began to rage with new chemistry. It was as if Morales had given me the philosopher's stone. "You'll probably start seeing colonies tomorrow," she said, handing it to me. Morales snapped the lid on the second dish and taped it shut. Opening the empty dish, she smeared a dollop across the sterile agar as if she were signing it. She moved it away from the flame, and after it cooled down she dipped it into the mush. She picked up a loop-a curled wire on a plastic handle-and stuck it in the flame of a Bunsen burner. One was sterile, and the other contained a cloudy mush rich with E. A graduate student named Nadia Morales put on purple gloves and set two petri dishes on a lab bench. On the third floor is a laboratory filled with nose-turning incubators and murky flasks. I got my dish of Escherichia coli on a visit to Osborne Memorial Laboratories, a fortress of a building on the campus of Yale University. On the bottom is a piece of tape labeled "E. I've made this species my guide-an oracle that can speak of the difference between life and lifeless matter, of the rules that govern all living things-bacteria, snowy egret, and curious human. They belong to a species that scientists have studied intensely for a century, that they understand better than almost any other species on the planet. Each of those spots is made up of millions of bacteria. On top of the agar lies a trail of pale gold spots, a pointillistic flourish. On the bottom is a layer of agar, a firm gray goo made from dead algae and infused with sugar and other compounds. A few beads of water cling to the underside of the lid. The box-a petri dish-looks lifeless compared with the biological riot outside my window. The biggest exception lives in the plastic box in my hand. Only a few species on the entire planet are exceptions to this rule. ![]() The other 98 percent of our DNA is a barely explored wilderness. They take up only about 2 percent of the human genome. Our ignorance actually reaches far beyond protein-coding genes. And yet scientists have no idea what a third of those genes are for and only a faint understanding of most of the others. Within this genetic tome, scientists have identified about 18,000 genes, each of which encodes proteins that build our bodies. We can now read the entire human genome, all 3.5 billion base pairs of DNA in which the recipe for Homo sapiens is written. We don't even know all that much about ourselves. Most other species on Earth are equally mysterious. How do all of the molecules in a snowy egret work together to keep it alive? That's a good question, made all the better by the fact that scientists have decoded only a few snips of snowy egret DNA. ![]() The fact that they live may be obvious, but what it means for them to be alive is not. All of these things have something in common with one another, something not found in rocks or rivers, in tugboats or thumbtacks. ![]() Stinkhorns and toadstools rudely surprise. An orange cat lurks under a lilac bush, gazing up at an oblivious goldfinch. Life fills my view: fescue and clover spreading out across the yard, rose of Sharon holding out leaves to catch sunlight and flowers to lure bumblebees. I GAZE OUT A WINDOW, a clear, puck-shaped box in my hand.
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