Microcosm – Carl Zimmer *****

In this book, Carl Zimmer explains how the bacterium Escherichia coli can be seen as a microcosm of life as a whole, and how, through studying E. coli, scientists have been able to learn a lot about the nature and evolution of all of life, including human beings. The book contains a surprising amount of material, given it is under 200 pages long, and turns out to be a model of great popular science writing.

It is remarkable how much we have been able to learn from E. coli, and in the earlier parts of the book, Zimmer explains how observations of the bacterium have contributed to our understanding of all of life. He describes the experiments, for example, which showed that genes are made of DNA and not protein, as many had previously thought; which confirmed the structure of DNA; and which allowed us to choose between Darwin’s theory of evolution and Lamarck’s theory of inherited characteristics. And, because E. coli can reproduce in only 20 minutes, we have been able to watch evolution in action, by placing colonies of E. coli under evolutionary pressure and observing useful mutations spreading throughout the colony.

The similarities between E. coli and ourselves and other species are emphasized throughout the book. Like us, for example, E. coli have sex and grow old, and the way they group together into what are called biofilms to perform specialist and complementary functions resembles the way cells in our bodies work together.

What struck me most, however, were not the similarities between E. coli and other species or even what it can tell us about life as a whole, but rather how interesting and complex E. coli is in its own right. I found it fascinating, for instance, how sophisticated E. coli’s mechanism is for controlling its temperature, and how E. coli navigate around the environment they find themselves in by using ‘microbial tongues’ as sensors. This complexity should not come as a surprise, however, Zimmer points out; E. coli are highly evolved and are just as modern as we are.

Zimmer aims to cover a lot in the book, and there are points where the content gets a little too technical for the nonspecialist. The section on genetic circuits in E. coli is quite challenging, for instance. But for the most part the explanations are wonderfully clear, and the fascinating nature of the subject matter would keep the interest of readers who may otherwise be tempted to skip the tricky parts.

In between the science the book gives us small insights into the lives of some of the scientists involved in studying the nature of E. coli, including Joshua Lederberg, Richard Lenski, Salvador Luria, and Jacques Monod, who famously said, ‘What is true for E. coli is true for the elephant,’ referring to E. coli’s ability to shed light on the rest of life. There are also useful discussions of some of the surrounding issues, like whether antibiotics will ever be manufactured which the harmful strains of E. coli and other bacteria will not be able to evolve resistance to; and how E. coli’s flagellum illustrates the power of natural selection, and does not suggest, as intelligent design’s supporters would argue, that there is ‘irreducible complexity’ in nature which required a designer.

The highlight of Microcosm, however, is at the end where Zimmer discusses the ethics of genetic engineering and the hybridization of species, especially where human tissue is involved, for the purposes of valuable research and drugs. In this thoughtful section, he suggests we should resist thinking that being human involves having an ‘inviolable essence’. He argues we should embrace perhaps the most important lesson E. coli can give us: like E. coli, we are already hybrids and, in an important sense, are not more than a combination of genes, some of which we have picked up from other species and even from viruses, shaped by our environmental influences.

All in all, then, a very entertaining read covering the science, the individuals behind it, and some of the wider debates and issues. I would definitely recommend it.

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Review by Matt Chorley