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On the serendipity of science

SIR ALEXANDER Fleming's discovery of penicillin depended on a series of serendipitous incidents. As a 16-year-old, Fleming played water polo for the London Scottish Volunteers and found himself competing against St Mary's Hospital, situated on the north side of Hyde Park. When Fleming decided to attend medical school a few years later, he chose St Mary's because it was the only one that he had ever come into contact with - a particularly fortuitous decision, as will become apparent.

It was at St Mary's in 1922 that a tear accidentally fell from Fleming's eye on to a bacterial culture. The next day, he was astonished to find that the place where the teardrop had fallen was free from bacteria. Teardrops contain an antibiotic enzyme called lysozyme, but unfortunately it is not particularly powerful against dangerous bacteria. So Fleming, inspired by the accidental teardrop, continued to search for a more powerful antibiotic.

Six years later, Fleming was still growing cultures of bacteria when he stumbled upon a dish with a distinct clear patch, indicating a site of dead bacteria. At its centre was a bit of mould that had apparently floated in through the window. The mould was a type of Penicillium, and Fleming called its antibiotic secretion Penicillin, a substance that has since saved millions of lives. He recognised his good fortune: "There are thousands of different moulds and there are thousands of different bacteria, and that chance put the mould in the right spot at the right time was like winning the Irish sweep."

Fleming's story has much in common with research being conducted by Agrol, a company that is trying to turn agricultural by-products into ethanol fuel. It has long been known that yeast can turn cornstarch and sugar cane into ethanol, but it would be more economic if we could find a talented bacterium that turned agricultural waste into ethanol.

Just such a bug floated into the laboratory of Brian Hartley at Imperial College in 1983. Belonging to a so-called thermophilic strain, the bacterium can operate at high temperatures and with great efficiency and can turn everything from paper pulping residue to milling waste into ethanol. Agrol is now testing a pilot plant with thermophilic bacteria at its core and hopes to eventually scale it up to a fully commercial biofuel reactor.

What gives this discovery extra resonance is that Imperial College is also next to Hyde Park, on the opposite side from St Mary's - in fact, both institutions were combined in 1988. Professor Hartley suspects that Hyde Park is home to a thriving colony of diverse bacteria capable of remarkable feats, and that neither his own fortuitous discovery nor that of Fleming would have happened had their laboratories been in the more concreted parts of London.

Simon Singh is the author of 'Fermat's Last Theorem' (Fourth Estate, pounds 6.99)