The field of biology has been wildly successful by taking what's called a reductionist approach, i.e., you tackle a small problem in isolation in order to gain insight into larger questions. In his new book, Microcosm: E. coli and the New Science of Life, Science writer Carl Zimmer took that reductionist approach and applied it to a pretty big issue: life itself. For Zimmer, the system that serves as a model of all life, and of humanity's often uncomfortable relationship to it, is the unprepossessing gut bacteria, Escherischia coli. Covering all of life is a big task, and Zimmer made the challenge that much harder on himself by choosing to target the book to a general audience. Still, he handles the challenge extraordinarily well.
Zimmer takes a historical approach his subject matter, zipping through the rich record of experiments that first identified DNA as the hereditary material and told us how the cell copies it and translates it into proteins. By necessity, he brings a few other organisms into his story, but E. coli and its viruses played a pivotal role in many of the classic experiments, so the digressions are short. From the basics, he rapidly expands into metabolism, cell division, and the complex circuitry that regulates gene expression.
Getting the basics down
Microcosm burns through a lot of information at a rapid clip. This pace is essentially unavoidable given the ground that Zimmer needs to cover, but many of the later chapters build on the earlier ones, so some material makes repeat appearances. For example, the flagella, which propels the bacteria through liquid environments, returns as an example of gene regulation, and again as part of a discussion of the Dover trial. Readers should be cautioned to take the first chapters slowly, because the information in them sets the stage for what follows. On the plus side, returning to some subjects in new contexts will probably help drive many points home.
With the basic biology in place, the book proceeds to describe the dizzying variety of organisms that all fall under the E. coli umbrella. Some versions live harmlessly in us our entire lives, while others trigger nation-wide recalls because of their lethal contamination of our food supply. Some are loners, others form complex communities in biofilms and commit a form of suicide that can be viewed as the cellular equivalent of altruism. Each one of the stories that Zimmer describes have come to light through dozens of complicated papers, but he manages to keep the focus on the complexity, chaos, and wonder of the big picture.
The same is true for chapters that describe E. coli's role in furthering our understanding of evolution; sophisticated concepts like horizontal gene transfer and error prone polymerases are all brought to bear on describing how fuzzy the barriers between species, strains, and individuals get at the bacterial level, and why these distinctions matter in terms of disease and drug resistance. As a biologist, this material nicely slotted into my existing knowledge base, but someone with a less extensive background will undoubtedly be leaping from one bit of new information to the next. Fortunately, each individual topic is beautifully explained, limiting the chances of it all getting overwhelming.
The fact that many of these are recurrent themes that are carefully woven throughout the work—evolution and horizontal gene transfer are pervasive—further lowers the risk of information overload. And even if many of the concepts don't completely stick, they will certainly leave the reader better equipped for reading more about biology. Or, given the frequency of E. coli contamination problems, following the news.
From our guts to the stars
The book takes an unexpected turn in the later chapters, though, as Zimmer moves from the basic understanding of life and into some of the ways that E. coli has helped transform the way that modern society looks at the subject. A detailed exploration of the bacterial contribution to the tree of life takes a detour into the Dover trial, where E. coli's flagellum played a starring role in demonstrating the difference between scientific studies and the contentions of the creationist movement.
For Zimmer, current controversies over stem cells and genetically modified food echo a past furor over the first genetically modified organism—E. coli. A full chapter is spent describing the controversy that followed science's first attempts at recombinant DNA, many aspects of which eerily parallel the current controversy over stem cells, right down to the people making the arguments. Zimmer points out that techniques that once sparked a furor now make us insulin without the slightest hint of an issue. He also reminds readers that the blurring of species boundaries, the wholesale exchange of genetic material, and the transformation of cells goes on in nature all the time (he's just spent the prior nine chapters describing it). In all, he makes a compelling case that much of the controversy is a gut reaction originating in some highly selective guts.
The final chapter of the book discusses how what we've learned about the limits of life on earth can inform our search for life elsewhere. Here, the topic cuts closest to the overall goal of Microcosm: a picture of the basic principles of life itself. But, as the title of the chapter highlights, we really have only one example of life, leaving us guessing about the basics and living in fear that when we reach other planets, E. coli might somehow have beaten us there.
Getting the science across
Science writing involves a series of trade offs. Complexity has to be simplified without throwing away meaning, immense topics need to be distilled without the loss of key information, and jargon has to be purged without replacing it with language that's even harder to follow. The net result is that it's essentially impossible to write a description of science that appeals to all audiences. With Microcosm, Zimmer hasn't quite managed the impossible, but he has done a very nice job.
Zimmer is a seasoned professional, having written several other books and contributed to National Geographic and The New York Times, among many other outlets. The experience shows as, even though the density of ideas is high, any individual aspect of biology that he discusses seems easy to grasp. Most science writers use metaphor to ease readers into complex concepts, but those in Microcosm seem richer and more descriptive than many others I've read. Here, for an example, is Zimmer's take on how bacteria create and harness a charge difference to make the cell's fuel, ATP:
Among the channels that decorate E. coli's membranes are pumps that hurl positively charged protons out of the microbe. E. coli gives itself a negative charge in the process, attracting positively charged atoms towards it. It draws some of them in to special channels that can capture energy from their movement, like an electric version of a waterwheel. E coli stores that energy in the atomic bonds of a molecule called adenosine triphosphate, or ATP.
I couldn't do a better job of describing this key process in the metabolism of all of life and, believe me, I've had to try.
Overall, Microcosm would be a valuable book for someone with a bit of knowledge of biology who's looking for a broad perspective on the field. It's short, but information-rich and written in a way that will reward those who read it carefully. On either of the extremes of that broad middle audience, there might be some problems. But regardless of your level of scientific knowledge, it's likely that the discussion of societal issues is a great reminder that very few of them are new, and how they were dealt with in the past can be instructive.