Most people don’t give bacteria much thought, except maybe when they’re horribly sick or buying probiotic yogurt. Bonnie Bassler, by contrast, has spent a whole lot of time thinking about bacteria.
The Princeton University molecular biologist has figured out that these tiny organisms communicate with one another, a finding that could have far-reaching implications, including the making of new medicines.
Bassler, who will be delivering an upcoming local Wall Exchange lecture, studies how bacteria “talk” to each other via chemical signals to act as a unit. In a phone interview with the Georgia Straight, Bassler explains that bacteria do miraculous things—some of which can be terrible, like causing disease, and some of which are fantastic, like helping to digest our food and keep us healthy—by working together.
“The way bacteria manage to do those things is they communicate with each other with chemical words,” Bassler says. “They count their numbers, and, by using chemical signals, they can recognize when there’s the right number of bacteria to do something together. They change behaviour to act in unison and accomplish tasks that they couldn’t accomplish with too few.”
Quorum sensing is the term used to describe this communication phenomenon, which is a kind of census-taking. “They vote with chemical votes,” says Bassler, who is working as an international visiting research scholar with Brett Finlay, a Peter Wall distinguished professor and a UBC microbiologist. “They recognize when the vote is counted and go along with the democratic decision-making process to carry out fantastic behaviours.”
Virulence is chief among those behaviours. Strength in numbers allows the microorganisms to mount potent attacks on people’s immune system. “It’s not like one bacterium can get in and dribble out enough molecules of a toxin to make you sick,” Bassler says. “Rather, they get in and wait and count themselves, then all launch these processes together. That’s why they’re so effective as pathogens.”
New medicines to combat deadly diseases could result from the development of quorum-sensing inhibitors, essentially “mutant” bacteria that can’t hear or talk to each other. This is especially promising given the growing medical problem of antibiotic resistance. The research breakthrough could also be put into practice by multiplying beneficial bacteria to do everything from helping plants grow to making biofuels.
“We also could make pro quorum-sensing molecules to make things better,” Bassler says.
Bassler became interested in the “social, secret lives” of bacteria when she was in graduate school several years ago. She attended a conference and heard geneticist Mike Silverman of the California-based Agouron Institute speak about bioluminescence, the biochemical emission of light in the ocean. Silverman was building on findings from the 1970s by Harvard scientist Woody Hastings, who discovered that when he grew bacteria in a flask, they didn’t produce light when they were in low numbers. But when they grew to a certain number, all of a sudden they turned on light simultaneously. It quashed the prevailing notion that bacteria were “asocial reclusives”, as Bassler puts it, and it got her even more excited about her studies.
“What was amazing about bioluminescence was that you could see this bacterial communication with your eyes,” she says. “When I heard Mike Silverman speak, I couldn’t imagine bacteria had the smarts to do those kinds of things. It was the most remarkable thing I’d ever heard.
“I literally ran up to him and said, ‘You have to let me be your postdoc,’ ” she recalls. “Once I got to his lab, I started to work out that there were multiple molecules involved and, ultimately, that quorum-sensing is widespread in the bacterial world and not restricted to one glowing bacterial species. They behave differently based on who is in the neighbourhood. It’s a lot like humans’ social behaviours.”
Aside from the potential applications of her research, Bassler says that her lab’s work shows how curiosity can have tremendous payoffs, a particularly important message to young people who may be considering a career in science.
“Scientists do things because they’re curious,” Bassler says. “They don’t necessarily have an application in mind. At first, we were wondering, ‘How does a bacterium know when it’s alone or in a group?’ Fastforward 20 years and the possibilities for pro and anti quorum-sensing molecules exist. That’s because I had the privilege of being allowed to be curious and to follow my nose without knowing this feature was going to happen.
“People love applications because they make our lives better, but you can’t have applications unless someone discovers something first,” she adds. “We have to give scientists the freedom to mess around.”
Bonnie Bassler will give the spring 2015 Wall Exchange lecture, “The Secret, Social Lives of Bacteria”, on Tuesday (May 26) at the Vogue Theatre. Tickets are free, but space is limited. Visit the Norethern Tickets website for details.