A Planet of Viruses - Carl Zimmer [12]
A clue to the true scope of viruses came in the middle of World War I. French soldiers were dying in droves, killed not just by Germans but also by bacteria. The microbes invaded their torn flesh, their food, and their drinking water. Their path was made easier by the worldwide flu epidemic in 1918. The flu weakened the defenses of its victims, allowing bacteria to infect their lungs. The soldiers spread the flu to civilians, and ultimately fifty million people died—many of them killed by bacteria.
Today, doctors can treat all of these bacterial infections with antibiotics. But antibiotics would not be discovered until the 1930s. During World War I, doctors could only treat battlefield infections by cleaning wounds and, if that failed, amputating limbs. Their patients often died anyway.
In 1917, in the midst of this carnage, the Canadian-born physician Felix d’Herelle discovered what seemed to him a medical miracle: a powerful substance that could wipe out bacteria. It was not an antibiotic. Instead, Herelle had discovered something that no one had ever imagined before: a virus that attacked not humans, or other animals, or even plants. He found a virus that made bacteria its host.
Herelle made his discovery while investigating an outbreak of dysentery among French soldiers. As part of his analysis, he passed the stool of the soldiers through a filter. The filter’s pores were so small that not even the bacteria that caused the dysentery, known as Shigella, could slip through. Once Herelle had produced this clear, filtered fluid, he then mixed it with a fresh sample of Shigella bacteria and then spread the mixture of bacteria and clear fluid in petri dishes.
The Shigella began to grow, but within a few hours Herelle noticed strange clear spots starting to form in their colonies. He drew samples from those spots and mixed them with Shigella again. More clear spots formed in the dishes. These spots, Herelle concluded, were bacteria battlegrounds in which viruses were killing Shigella and leaving behind their translucent corpses. Herelle believed his discovery was so radical that his viruses deserved a name of their own. He dubbed them bacteriophages, meaning “eaters of bacteria.” Today, they’re known as phages for short.
The concept of bacteria-infecting viruses was so strange and so new that some scientists couldn’t believe it. Jules Bordet, a French immunologist who won the Nobel Prize in 1919, became Herelle’s most outspoken critic after he failed to find phages of his own. Instead of Shigella, Bordet used a harmless strain of Escherichia coli. He poured E. coli–laden liquid through fine filters, and then mixed the filtered liquid with a second batch of E. coli. The second batch died, just as they had in Herelle’s experiments. But then Bordet decided to see what would happen if he mixed the filtered liquid with the first batch of E. coli—that is, the one he had filtered in the first place. To his surprise, the first batch of E. coli was immune. Bordet believed that his failure to kill the bacteria meant that the filtered fluid did not contain phages. Instead, he thought, it contained a protein produced by the first E. coli. The protein was toxic to other bacteria, but not to the ones that made it.
Herelle fought back, Bordet counterattacked, and the debate raged for years. It wasn’t until the 1940s that scientists finally found the visual proof that Herelle was right. By then, engineers had built electron microscopes powerful enough to let scientists see viruses. When they mixed bacteria-killing fluid with E. coli and put it under the microscopes, they saw that bacteria were attacked by phages. The phages had boxlike shells in which their