Genesis Machines: The New Science of Biocomputing

by Martyn Amos

353pp, Atlantic, £18.99

If you thought molecular biology was an earnest business, look here: a scientist has coaxed strands of DNA into forming countless tiny smiley faces, a hundred times smaller than a red blood cell. Haunting! Reproduced photographically in this book is the smallest smile ever made, looking almost as though it belongs to a benign alien intelligence. Humans love to read faces into clouds or rock formations on Mars; now they can imprint their features in the submicroscopic netherworld. The researcher's boss declared: "In a typical reaction, he can make about 50 billion smiley faces. I think this is the most concentrated happiness ever created." The optimism of the rave generation lives on.

Amos's fascinating book shows how such miniature manipulation is a step on the road to "truly programmable matter". Researchers dream of a microscopic "doctor" robot that travels around in your bloodstream and dispenses drugs at the first sign of illness. But it will not be a submarine shrunk by a miniaturising ray, as in Fantastic Voyage; it won't be electronic at all. Why reinvent the wheel? Nature's "machines" already contain the components we need. "Science-fiction authors tell stories of 'microbots' - incredibly tiny devices that can roam around under their own power, sensing their environment, talking to one another and destroying intruders," Amos notes. "Such devices already exist, but we know them better as bacteria."

Amos, who was awarded the first ever PhD in "DNA computing", takes us on a canter through computer history. The legendary mathematician Alan Turing, hero of Bletchley Park, described a universal computing device now known as a Turing Machine: a box that reads inputs off a long skein of tape, performs algorithms on the data, and outputs an answer. It turns out that biology functions in an amazingly similar way: a molecule "head" reads the "tape" of one strand of a DNA double helix and "writes" the complementary base on to a new strand. "Jeez," one researcher remembers thinking, "these things could compute."

A decade ago, people began trying to build computers on this basis. What do such computers look like? Well, like liquid sloshing around in a test tube. Set up your problem, and trillions of molecules will nearly instantaneously find a huge range of possible answers. The trick is in picking out the right one. Amos describes such experiments beautifully, combining laboratory drama with technical explanations of techniques for splicing and bolting together bits of DNA. It's rather like super-complex Meccano.

After a while, however, it becomes clear that the approach needs to be more structured. We need a set of "biobricks" to build stuff with. From Meccano to Lego. Here is a microbial camera that uses bacteria as pixels. And the really cool part is "self-assembly". IKEA self-assembly furniture is mournfully misnamed, as it does not actually build itself. But that's what, for instance, a pair of sticky DNA tweezers does. Maybe one day the technique could be scaled up to shelving units.

Once you have built a molecular computer that has the same sort of error-correction, support, repair and replication functions as, say, a human cell, what have you done? You have, perhaps, created life from the ground up. Dr Frankenstein had nothing on the new generation of "biohackers". Biohackers are like computer hackers, but instead of fiddling with, say, website code, they are fiddling with the "code of life". Cue a new generation of complaints about scientists playing God.

And, as Amos admits, there are legitimate concerns about the new technology. Researchers have tried to build safety catches into their work by giving, for example, killer genes to their designer bacteria, so that the bugs automatically die after a set period. The problem is that evolution finds a way around it: a mutant copy of the killer gene arises that doesn't work properly, and a new generation of the little monsters lives on. This was entirely predicted, says Amos happily of the experiment, which is not perfectly reassuring. Evolution can also be harnessed, on the other hand, by building a rough version of the system you want and then letting it mutate into the most efficient configuration. Of course, you wouldn't want this stuff escaping into the wild. Amos ends on the sensible note that, like any disruptive technology, biocomputing requires rational political discussion and supervision. Well, we can hope.

The book also shows how hard it is to get away from the constant application of engineering metaphors, such as Amos's claim that genes are "computing components", and anthropomorphic language, as when it is said that ribosome works by "interpreting mRNA messages". This is manna to creationists, who insist that where there is a computer, there must be someone who designed it. Amos skips lightly over such philosophical problems, but it is a serious question whether appeals to "self-organisation" or "information" are themselves in some sense metaphysical, even if one rejects the epistemological nihilism of "Intelligent Design". Understandably, however, Amos is more of the pragmatic scientist's persuasion: sure, there's a mystery here - so let's tinker around and try to solve it. His lucid and punchy prose conveys a genuine excitement of the frontier. It is even possible that, when the footnote numbering goes crazy on pages 199-201, it is some sort of joke about genetic mutation. Sadly, I was not able to find meaning in the resulting number series.

· Steven Poole's Unspeak is published by Little, Brown