Listening to Bacteria

By studying microbial communications, Bonnie Bassler has come up with new ways to treat disease

"Bacteria can talk to each other," says Bonnie Bassler. "Not only can they talk, but they are multilingual." And she knows how to speak their languages. (Richard Schulman)
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Bonnie Bassler, her shoes kicked off, knees up and socked feet pressed against the rim of the conference room table, watches with an air of droll expectation as a researcher in her world-renowned microbiology laboratory at Princeton University stands up to present his latest experimental results to the other members of her team. Yunzhou Wei is known for his campy presentations, and he does not disappoint. Slides of the cast members of his favorite television crime series flash on the screen and he launches a brief, sportive discussion of the lessons the scientists might extract from the shows: Trust your instincts! But look for evidence, too! Then a far more pressing question arises: which TV character would Bassler want to play? The genius behavioral analyst? No, no, not the “nerdy guy,” Bassler grumbles. Well, how about the prim and pretty forensic anthropologist? No, the celebrated scientist’s mind is made up. “I want to be her,” Bassler says, pointing at Special Agent Jennifer “JJ” Jareau, the Nordic bombshell on the CBS program “Criminal Minds.” Case closed, Bassler says. “Let’s get back to molecules now.”

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The character of Jareau suits Bassler remarkably well. Jareau is the communications point person of her group, the media liaison between the FBI and the outside world. Bassler, 48, has been fabulously successful in her career, winning laurels like a MacArthur Foundation “genius” award, membership in the National Academy of Sciences, a coveted position with the Howard Hughes Medical Institute and the presidency of the American Society for Microbiology. And all that can be traced to her deep appreciation for the power of communication. Messaging is the medium in which Bassler shines.

Bassler is at the forefront of the fast-growing field of “quorum sensing,” the study of how microbes communicate with each other as they go about building the vast interlocking infrastructure of life on which we macrobes depend. In recent years she and other microbiologists have discovered that bacteria are not the dull solipsists of long-standing reputation, content to merely suck in food, double in size, divide down the middle and repeat ad infinitum, attending to nothing but their obtuse, unicellular selves. Instead, bacteria turn out to be the original newshounds, glued to their cellphones and Internet chat lines. They converse in a complex chemical language, using molecules to alert one another to who’s out there, in what numbers and how best to behave given the present company. Bacteria survey their ranks, they count heads, and if the throng is sufficiently large and like-minded—if there is a quorum—they act. Through chemical signaling, tiny bacterial cells can band together and perform the work of giants. They can compost an elephant, fertilize an oak forest or light up the oceans in the eerie teal glow of bioluminescence. Some bacterial collusions are far less charming and do real harm. Molecular communication allows 600 different species of bacteria to organize themselves into the slimy dental plaque that leads to tooth decay, for example, and it likely enables the nasty pathogens that cause streptococcal pneumonia or bubonic plague to time the release of their toxins for maximum impact on their human hosts.

In deciphering the nuances of bacterial communication, biologists have learned that the lexicons come in two distinct styles: private and public. Every bacterial species has its own dialect, a molecular signature that can be understood only by others of its kind. Bassler made her fame discovering that bacteria also traffic in the second, more universally recognized set of signals that seems to serve as bacterial Esperanto. “Bacteria can talk to each other,” she says. “Not only can they talk, but they are multilingual.”

“Bonnie is the champion of bacterial conversations,” says Richard Losick, a microbiologist at Harvard University. “This is a field that goes back to the 1970s, but she has re-energized it in a remarkable way.”

“Her work is groundbreaking,” says Jo Handelsman, a microbiologist at Yale University. “We used to think of bacterial communication as something species specific, but she’s really opened up the possibility that interspecies communication is a big part of the quorum-sensing story.”

Amusingly enough, the scientist who helped divulge that bacteria are polyglot is herself...not. “What do you expect?” she mutters. “I’m an American! I speak English!”

Bassler’s foray into microbial idioms is of more than academic interest. The work may well have an impact on what the Centers for Disease Control and Prevention calls one of the “most pressing public health problems” in the world today: antibiotic resistance. In recent years, the overuse of drugs like penicillin to treat childhood earaches, or to inoculate livestock crowded together on factory farms, has spawned the appearance of “superbugs,” bacterial strains able to shrug off virtually any of the conventional antibiotics lobbed at them.

Bassler and her peers are guardedly optimistic that their insights into the circuitry of quorum sensing will eventually yield a new, safer generation of antibiotics. Rather than seeking to kill bacteria outright, as current antibiotics do—an approach that readily leads to drug resistance—the novel therapeutics would simply muzzle the molecular messages that induce bacteria to cause disease. Bassler explains the difference between the two approaches this way: “Let’s say I’m a bacterium, and you’re hitting me with a drug like penicillin that pops the bacterial membrane, but I happen to have a mutation that makes me impervious to that popping effect,” she says. “No question about it, I’ll have an immediate growth advantage.”

But let’s say you are instead using an anti-quorum-sensing drug designed to inhibit bacterial communication, she continues, “and I’m a bacterium with a mutation that makes me immune to the blocker.” Great: I’m a microbe that’s trying to get in touch with my friends, but because of the blocker, nobody around me is listening. If virulence depends on effective bacterial communication, she says, my lone little mutation will give me no growth advantage at all: “What good does it do me?”


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