Book of the week: March of the Microbes

From the first glimmers of consciousness until the day before yesterday, humans had no notion that the majority shareholders in life on Earth even existed. The unveiling of the profusion of microbes that began a few hundred years ago is one of those simple, empirical discoveries that is as unexpected as it is irrefutable.

As such, it might have induced a shift in world view. But that did not quite happen. The notion that disease was spread by an ill-defined miasma carried over into the triumphs of germ theory in the 19th century to cement an association between microbes and dirt. Medicine's discovery of hygiene and antisepsis, reinforced by the efforts of advertisers, means that germs still seem mostly somewhat sinister or distasteful. Apart from a few "friendly" microbes, which give us bread, cheese and beer, the ones we know about bring disease, decay and putrefaction. The vast majority of microbial species, which simply get on with running the world, pass us by.

After all this time, and in the wake of a welter of fresh discoveries almost as arresting as the initial sightings of microbes, could this mean that there has been something missing in the popularisation of the subject? If so, it is not for lack of trying. Here, John Ingraham gives it his best shot. His book is surely born of an impulse felt by many a career microbiologist. After a lifetime appreciating the wonders of the microworlds that harbour most living things - in Ingraham's case taking in a stint as president of the American Society of Microbiologists and a professorship (now emeritus) at the University of California - it is time to tell everyone else what they are missing.

How well does he do it? Engagingly enough, on the whole. The author roams the microbial realm and brings back treasures old and new. We learn why the Black Sea is black, how the bubbles get into champagne, and why only saltwater fish smell fishy. More unexpectedly, it turns out that the largest known living thing began as a microbe (a fungus in the forests of Oregon that started small, but has grown over 2,400 years to cover 3.4sq miles).

More familiar not-quite-so-large organisms, too, have microbial affinities - the mitochondria that provide energy in our own cells and the chloroplasts that harvest solar energy in plants both began, aeons ago, as symbiotic bacteria. On the very largest scale, the whole biosphere is shaped by microbial action. They run the nitrogen and carbon cycles on which other life depends, in vast ecological transactions whose details are still being worked out. One of the major microscopic contributors to replenishing atmospheric nitrogen was discovered only in the 1990s.

So there is a wealth of good stories here. Set against this are a few flaws that betray Ingraham's lack of experience as a popular writer. He really ought to provide a simple elucidation of the chemical terms oxidation and reduction, for example, before using them throughout as the keys to microbial energy release. His description of the role of proton gradients across membranes is a bit woolly (the fact that he also writes about "one megawatt of energy per hour" indicates that, while an ace microbiologist, he is no physicist). The recitation of species names also gets a little tedious for the non-specialist. And there are a few digressions into topics such as sulphur mining that clearly interest the author but have little to do with his subject.

Beyond that is an expository problem that would challenge any writer. Ingraham's stories, if they have a theme, are designed to add up to a picture of unsuspected diversity. Although he takes us on a tour of various landscapes to look at their microscopic fauna (99 per cent of microbes cannot be grown in the lab), the look is with the unaided eye. Microscopic beauty, where it exists, is not apparent. We are invited to contemplate a collection of slimes, smears, blooms and tints - coloured patches of this or that. The device wears a little thin.

Go down to the microscopic level, though, and the details that come into focus are still problematic for a writer. Among these myriad organisms, wondrous though they are, biodiversity expresses itself mainly through wild variations in metabolism, rather than the morphology or behaviour we notice so readily among larger life forms. So we get lots of details of chains of chemical action and reaction, mediated by enzymes that microbes have evolved to meet this or that peculiar circumstance. This is fascinating to anyone who is biochemically curious, but possibly less so to those who are not already primed to enjoy following neat tricks that move just the right atom from one molecule to another.

These myriad features of the subject have induced others to explore different angles on microbial stories. The British authority John Postgate, a leading academic and a felicitous stylist, arranged microbial vignettes around one possible theme in his classic Microbes and Man, first published in the 1960s. As the extraordinary range of microbe habitats became clearer in subsequent decades, he pulled them together around the new theme of life at the extremes in the 1994 book The Outer Reaches of Life, detailing how some species flourish in super-heated or super-cooled environments, or under high pressure or in salt solutions fatal to other organisms.

More ambitious was the American Lynn Margulis, who marshalled the evidence for the origin of mitochondria and chloroplasts as symbiotic bacteria, and used a grander narrative in her Microcosmos: Four Billion Years of Evolution from Our Microbial Ancestors (1987), written with her science writing son Dorion Sagan. They showed the evolution of life with bacteria centre stage - on the basis that "life on Earth is such a good story that you can't afford to miss the beginning".

Most recently, the fine science writer Carl Zimmer used a single microbe that loves the lab - the much-studied E. coli - as the centrepiece of his 2008 title, Microcosm: E. Coli and the New Science of Life, which explored what one simple life form can tell us about life in general.

Ingraham's book has elements of all of these. He tells us a little of E. coli, and quite a lot about the metabolic tricks of bacteria that live in extreme environments. He has lots of examples of the cooperative ways of living that many bacteria have evolved, and which Margulis offers as a counter to the simple Darwinian picture of relentless individual struggle. Ingraham also surveys the ways microbes serve human ends, as well as their crucial roles in ecosystems everywhere from forests and fields to deserts and arctic seas.

And he combines many of the older stories with more up-to-date findings, especially those concerning microbes' continual exchange of genes, and the extent of the (as yet largely uncharted) diversity of species - and genes - in the biosphere, especially in the ocean and the soil. This broad mix of themes and ideas is still the easiest way to give a good flavour of microbiology. It resembles that conveyed in another classic effort, Bernard Dixon's Power Unseen, which was compiled from a magazine's "microbe of the month" series. But the decision not to highlight one theme, and instead to relate many small stories rather than one big story, does give the book a slightly old-fashioned feel.

March of the Microbes is a worthy addition to the annals of popularisation. But it is still not the one, I think, from which readers will come away with their view of the world deeply changed.

THE AUTHOR

John Ingraham is professor emeritus of microbiology at the University of California, Davis. He was chair of the College of Agriculture, which became the department of microbiology at Davis.

As a teacher, he loved introductory courses. A book biography says: "He hopes to create the same fascination with the microbial world in his students that he discovered in the introductory course."

Now retired, Ingraham has a companion with whom he "travels, hikes and compares notes about the world". He backpacks in the Sierra Nevada, where he drinks water "from lakes and streams above about 8,000ft". Music is another passion: "I listen incessantly to classical music, although I've learned (painfully) I have no talent for playing it."

He writes avidly, working on a new book and contributing to Wines and Vines magazine. At home, when not tending the chickens in his back garden, he enjoys the company of a "dwindling group" of friends.