Microcosm_ E. Coli and the New Science of Life - Carl Zimmer [2]
Bacteria were particularly mysterious in Escherich’s day. They seemed fundamentally different from animals and other forms of multicellular life. A human cell, for example, is thousands of times larger than E. coli. It has a complicated inner geography dominated by a large sac known as the nucleus, inside of which are giant structures called chromosomes. In bacteria, on the other hand, scientists could find no nucleus, nor much of anything else. Bacteria seemed like tiny, featureless bags of goo that hovered at the boundary of life and nonlife.
Escherich, a forward-thinking pediatrician, accepted a radical new theory about bacteria: far from being passive goo, they infected people and caused diseases. As a pediatrician, Escherich was most concerned with diarrhea, which he called “this most murderous of all intestinal disease.” A horrifying number of infants died of diarrhea in nineteenth-century Germany, and doctors did not understand why. Escherich was convinced—rightly—that bacteria were killing the babies. It would be no simple matter to find those pathogens, however, because the guts of the healthiest babies were rife with bacteria. Escherich would have to sort out the harmless species of microbes before he could recognize the killers.
“It would appear to be a pointless and doubtful exercise to examine and disentangle the apparently randomly appearing bacteria,” he wrote. But he tried anyway, and in that survey he came across a harmless-seeming resident we now call E. coli.
Escherich published a brief description of E. coli in a German medical journal, along with a little group portrait of rod-shaped microbes. His discovery earned no headlines. It was not etched on his gravestone when he died, in 1911. E. coli was merely one of a rapidly growing list of species of bacteria that scientists were discovering. Yet it would become Escherich’s great legacy to science.
Its massive, luxurious growth would bloom in laboratories around the world. Scientists would run thousands of experiments to understand its growth—and thereby to understand the fundamental workings of life. Other species would also do their part in the rise of modern biology. Flies, watercress, vinegar worms, and bread mold all had their secrets to share. But the story of E. coli and the story of modern biology are extraordinarily intertwined. When scientists were at loggerheads over some basic question of life—what are genes made of? do all living things have genes?—it was often E. coli that served as the expert witness. By understanding how E. coli produced its luxurious growth—how it survived, fed, and reproduced—biologists went a great way toward understanding the workings of life itself. In 1969, when the biologist Max Delbrück accepted a Nobel Prize for his work on E. coli and its viruses, he declared, “We may say in plain words, ‘This riddle of life has been solved.’”
THE UNITY OF LIFE
Escherich originally dubbed his bacteria Bacterium coli communis: a common bacterium of the colon. In 1918, seven years after Escherich’s death, scientists renamed it in his honor. By the time it got a new name, it had taken on a new life. Microbiologists were beginning to rear it by the billions in their laboratories.
In the early 1900s, many scientists were pulling cells apart to see what they were made of, to figure out how they turned raw material into living matter. Some scientists studied cells from cow muscles, others sperm from salmon. Many studied bacteria, including E. coli. In all of the living things they dissected, scientists discovered the same basic collection of molecules. They focused much of their attention on proteins. Some proteins give life its structure—the collagen in skin, the keratin in a horse’s hoof. Other proteins, known as enzymes, usher other molecules into chemical reactions. Some enzymes split atoms off molecules, and others weld molecules