In February 1982, physicians in Medford, Oregon encountered an unknown pathogen that waged a sort of intelligent biochemical warfare against our bodies. After being ingested, the rod-shaped bacteria—small enough to fit 500 of them side-by-side across the diameter of a single period in twelve-point font—were able to monitor their surroundings for human hormones to determine where they were inside their victims. When they received the signal that they had reached the intestines, the rods sprouted tails that operated as proton-powered outboard motors, swam towards one another, and constructed their nano-weapons: syringes small enough to pierce human cells and deliver injections of treacherous chemical instructions.
The affected cells responded to the injections like mind-controlled doppelgangers. Their membranes deformed into landing pads, making it easier for their rod-shaped masters to sup on them as their internal fluids and molecules started to leak. In some cases, the rods also released toxins that spread through the rest of the victims’ bodies, tinkering with cells from the inside and causing them to explode.
This particular pathogen, known as serotype O157:H7 of the bacteria Escherichia coli, or E. coli 157 for short (the variety behind the spinach and beef food-poisoning scares of 2006 and 2007), is one of the many strains chronicled in science journalist Carl Zimmer’s latest book, Microcosm: E. coli and the New Science of Life (Pantheon Books). (The most recent American tomato/jalapeño scare is due to Salmonella, a distinct, but closely-related bacteria that split off from E. coli back when dinosaurs were still walking the earth.)
It may seem like devoting an entire book to one family of single-celled organisms is a bad idea. It’s an election year, after all, and with two wars, a tanking economy, and a warming planet to deal with, bacteria may seem distracting. But Zimmer is no ordinary science writer: he hosts a Web site where he posts photos of science tattoos, writes one of the best and longest running science blogs on the Web, and, in 2001, wrote a book that made parasites seem fascinating, elegant, and frightening all at once.
E. coli itself is a fascinating species. Its manifestations comprise the killers Shigella and O157:H7, as well as innocuous laboratory varieties like K-12 (“[S]o harmless that scientists make no efforts to protect themselves from it; instead, they have to protect it from fungi and bacteria.”), among many other strains. E. coli can build microscopic weapons and wage war, and yet without the beneficial strains living in our gut we might not be able to survive. When scientists started experimenting with genetic engineering, it was E. coli they worked with. And as futurists and computer scientists look for a link between life as we know it and artificial networks like the Internet, it is in the natural functioning of E. coli that they see something of a bridge.
Zimmer covers a lot of ground in Microcosm, and the book runs in chronological order, from E. coli’s discovery by the German pediatrician Theodor Escherich in 1885, right up to the current debate about biotechnology and the ethical implications of engineering “chimeras” like animals with partially human organs.
What’s great about Zimmer’s approach is that he takes the time to introduce the reader to the scientists and experiments that changed our understanding of E. coli and biology in general. Early on, he sets the tone of the book with a narrative account of one of the more seminal studies in the bacteria’s history—the one that showed that a single bacterium could actually swap genes rather than just clone its own through asexual cell division. It’s the story of a young student named Joshua Lederberg and two mutant strains of E. coli:
Lederberg started work at Yale in 1946. He selected a mutant strain that could make neither the amino acid methionine nor biotin, a B vitamin. The other strain he picked couldn’t make the amino acids threonine and proline. Lederberg put the bacteria in a broth he stocked with all four compounds so that the mutant microbes could grow and multiply. They mingled in the broth for a few weeks, with plenty of opportunity for hypothetical sex.
Lederberg drew out the samples of the bacteria and put them on fresh petri dishes. Now he withheld the four nutrients they could not make themselves: threonine, proline, methionine, and biotin. Neither of the original mutants strains could grow in the dishes. If their descendents were simply copies of their ancestors, Lederberg reasoned, they would stop growing as well.