Teamwork Makes the Dream Work for People and Bacteria

Three scientists will share a Canada Gairdner Award for their pioneering work in understanding how bacteria communicate via a chemical language.

 |  Transcript [PDF]

Collaboration is an important part of scientific research, with scientists often coming together to combine their efforts and contribute towards shared scientific goals. As it turns out, collaboration is also an important trait amongst bacteria.

By communicating through a chemical language, and waiting until they have the right numbers, bacteria can be successful at tasks they wouldn’t have been able to accomplish on their own.

For this foundational discovery — a process known as quorum sensing — three scientists and longtime collaborators were named 2023 Canada Gairdner International Award laureates. The award was shared between Bonnie Bassler, Squibb Professor and Chair of the Department of Molecular Biology at Princeton University; E. Peter Greenberg, Nester Professor of Microbiology at the University of Washington; and Michael R. Silverman, a former Adjunct Professor of marine biology at Scripps Institute of Oceanography who retired in 2000.

The power of cooperation

It all started with an obscure bioluminescent marine bacterium known as Vibrio fischeri, which exhibits a particularly unique trait: it only lights up when it’s in a group. This behaviour was first characterized in the 1970s by the late J. Woodland Hastings, a professor at Harvard University, who described a signalling chemical of unknown structure responsible for the behaviour.

“There was a 10-year period where we thought this was happening, but nobody knew how,” Greenberg says. “And then one of my co-recipients, Mike Silverman, together with one of his graduate students, discovered the genes responsible [for this mechanism].”

“Genetics is a very powerful tool,” Silverman adds.

Greenberg, who had been training with Hastings, further characterized these genes independently. He also discovered a similar chemical signal in the pathogenic bacterium Pseudomonas aeruginosa. This is when the term quorum sensing, which describes this cell-to-cell communication, was born.

“[W]hat we and others have shown is that [bacteria] communicate with a chemical language. They count their numbers and they recognize when they have the right numbers,” explains Bassler.

To do this, bacteria secrete small molecules known as autoinducers. When a large enough group of bacteria have gathered, and enough autoinducers have been secreted, the bacteria can detect this chemical signal and start to work together as a group.

“If [bacteria] all do something together, they can be successful at tasks that they couldn’t accomplish if they acted as individuals. Because individually, they’re too small to make a difference,” Bassler continues.

Bassler — who once worked as a postdoctoral researcher with Silverman — brought these insights to a new level by demonstrating that this phenomenon is not obscure, but is instead common among bacteria.

In fact, the researchers discovered that quorum sensing behaviour is not limited to bacteria at all. Bassler also showed that bacteria can use this mechanism to communicate across species, and that it underlies bacterial interactions with viruses.

A new field of microbiology

Today, quorum sensing has emerged as a new field of microbiology. The discoveries made by Bassler, Greenberg, and Silverman not only changed our understanding of bacteria and their interactions with each other, but also opened the doors to using cell-to-cell communication in clinical settings.

As an example of this, Bassler and her collaborators have used quorum sensing to develop small-molecule therapies, which are less vulnerable to antimicrobial resistance than traditional antibiotics. Greenberg has also used quorum sensing to combat infections associated with cystic fibrosis.

Overall, the laureates agree that collaboration was a crucial aspect of their discoveries. By working together and building off each other’s ideas, Bassler, Greenberg, and Silverman have revolutionized the field of microbiology.

“It’s funny that the prize is for figuring out how groups of microbes […] work together and optimize behaviours, because that’s what we’re trying to do in the lab,” Bassler says.

“I find that […] kind of magical about the prize.”

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Bonnie Bassler is a Howard Hughes Medical Institute Investigator and the Squibb Professor and Chair of the Department of Molecular Biology at Princeton University. She grew up in northern California. As a young person, she adored nature and animals and hoped to be a veterinarian when she grew up. However, she became fascinated with biochemistry and molecular biology when she went to college, so she switched direction. Bonnie received a BS in Biochemistry from the University of California at Davis and a PhD in Biochemistry from the Johns Hopkins University. She performed postdoctoral work with Michael Silverman in Genetics at the Agouron Institute. Basler joined the Princeton faculty in 1994. Her research focuses on molecular mechanisms that bacteria use for intercellular communication; a process called quorum sensing. Bassler’s discoveries are paving the way to novel therapies to combat disease-causing bacteria. She received prizes including a MacArthur Foundation Fellowship, the Shaw Prize in Life Sciences and Medicine, the Dickson Prize in Medicine, the Gruber Genetics Prize, and the Wolf Prize in Chemistry. Bassler received Princeton’s President’s Award for Distinguished Teaching. She is devoted to diversity in the sciences and educating lay people about the thrill and relevance of scientific research. Bassler was President of the American Society for Microbiology, and she served on the National Science Board. She was nominated to the Board by President Barack Obama. The Board oversees the NSF and prioritizes the nation’s research and educational activities in science, math, and engineering.

Everett Peter Greenberg was born in Hempstead, New York, on November 7, 1948. He received his Bachelor’s degree in Biology from Western Washington University in 1970 and PhD in Microbiology in 1977 from the University of Massachusetts. After finishing his postdoctoral at Harvard University (1977-1978), he joined the faculty at Cornell University Microbiology (1978-1984). He later moved to the University of Iowa as Professor of Microbiology (1988-2000) and Shepperd Professor of Microbiology (2000-2005), finally joining the University of Washington in 2005 where he currently is the Nester Professor of Microbiology. Greenberg has studied quorum sensing since the late 1970s and is widely considered the father of the field of microbial quorum sensing. The term “quorum sensing” originates in a 1994 Journal of Bacteriology article on which he was senior author. Greenberg is a Fellow of the American Academy of Arts and Sciences, and Fellow of the National Academy of Sciences.

Michael “Mike” Silverman was born October 7, 1943 in Fort Collins Colorado. He was the son of a rural veterinarian who practiced in western Nebraska, USA. In high school, Silverman studied vocational agriculture and later worked on an experimental farm where he developed an interest in plant diseases and bacteriology. He received BS (1966) and MS (1968) degrees in Bacteriology from the University of Nebraska. In 1972, Mike completed a PhD from the University of California, San Diego studying the molecular genetics of motility and chemotaxis in Escherichia coli.
This work required the application of classical and modern genetic methods such as DNA cloning and sequencing, gene product programming and transposon mutagenesis. He continued research as an independent scientist at the Agouron Institute and as an Adjunct Professor of marine biology at Scripps Institute of Oceanography in La Jolla California. There, he investigated motility and bioluminescence in marine bacteria. In particular, work with JoAnne Engebrecht and Bonnie Bassler resulted in the discovery of fundamental genetic mechanisms that control bioluminescence. These mechanisms were later found to control many different functions in many species of bacteria. Mike retired to the mountains of Wyoming in 2000.

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