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Faculty Research in the News

Bacteria and the power of teamwork

Courtesy of Princeton University Office of the Dean for Research
How do simple bugs thrive? It's all about quorum-sensing. Tess Shellard, in her winning essay for the Wellcome Trust Science Writing Prize, explains.
Hawaiin Bobcat
The Hawaiian bobtail squid hosts bacteria that light it up at night.
Photograph: Nick Hobgood

Imagine for a moment that we all have one firework and our sole purpose is simply to light it. With just one trick to last a lifetime, how would you use it? Setting it off randomly would achieve very little; few would even see it. But if you took a lesson from bacteria you would gather together to light them all at once, and illuminate the whole sky.

Bacteria play a crucial role in life on this planet. They digest our food, synthesise our vitamins, help to make our wine and cheese.

Others are deadly, the cause of numerous diseases. But how have these single-celled organisms taken charge when they have no ears to hear, no sense of touch and no central intelligence to organise their assault? Their secret lies in teamwork. Each bacterium can secrete a chemical that can be read only by members of the same species; the concentration of this chemical can tell it how many of its siblings are nearby. This ability, called quorum-sensing, helps the bacteria to time how and when they express their genes. They don't just act; they wait until there are enough of them for the action to be effective and co-ordinate their moves.

Not only can a bacterium tell if kin are near, it can tell if it is among different types of bacteria, allowing it to build alliances that can help them all to thrive.

Professor Bonnie Bassler of Princeton University's department of molecular biology has led the research on quorum-sensing. She found that the Hawaiian bobtail squid hunts safely at night thanks to the quorum-sensing abilities of a bacterium called Vibrio fischeri. By day, the squids bury themselves in the sand, coming out at night to hunt in the shallows. But they cast a shadow in the moonlit waters, which can leave them vulnerable to predators. Enter the Vibrio fischeri. These live in a sac in the squids' mantles and, when there are enough of them, they switch on a light. Their bioluminescence disguises the squid's silhouette on the sea bed. To get it just right, sensors on the squid's back gauge the strength of moonlight, with filters adjusting the light emitted from the sacs.

In return for all this handy illumination, the bacteria are kept well-fed. In the morning, the squid purges itself of its visitors and, as the bacteria's numbers drop below the quorum threshold, they turn off their light. The remaining population then do what they do best and multiply throughout the day, reaching sufficient numbers by nightfall to start glowing all over again.

Not all bacteria are quite that endearing – chancing upon the wrong kind can be deadly. Modern medicine has allowed us to blitz anything lethal to us with antibiotics, but this has led to problems, too, bringing a rise in superbugs – bacteria resistant to drugs. Knowing about quorum-sensing, however, can offer hope. It is possible to interfere with the communication between individual bacterial cells in order to ensure that they live out their days without getting too dangerous. As each species has its own language, we can befuddle one without disturbing the rest. On the other hand, we could interfere with helpful bacteria to increase the volume of their conversation and increase their activity.

When it comes to life on Earth, we like to think that the bigger the brain, the better. Bacteria might be small but they communicate in more than one language, they strategise, they co-ordinate their efforts, they have thrived in places you wouldn't even go for a dare. It seems clear the bacteria still have a lesson or two for us big-headed folk.

The inaugural Wellcome Trust science writing prize, in association with the Guardian and the Observer, was judged by: Alan Rusbridger, editor-in-chief of Guardian News & Media; Robin McKie, science editor of the Observer; Sir Mark Walport, director of the Wellcome Trust; Clare Matterson, director of medical humanities and engagement at the Wellcome Trust; and Dara O Briain, broadcaster and comedian.

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