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Bacterial attraction

Bad things can happen when bacteria stick to surfaces. Everything from medical instruments to airplane parts to human teeth can be degraded. Ruby Sullan has a passion for discovering what makes these bacteria stick. (Photo by Ken Jones)

What’s a single microbe like you doing sticking to a surface like this? 

That’s the question Ruby Sullan asks each time she steps into her laboratory in the new Environmental Sciences building at University of Toronto Scarborough.

Sullan, a biophysical chemist, studies the mechanisms that cause a single bacteria cell or lone molecule to adhere to a particular surface. She has a deep drive to know what make them stick.

“My technique involves an atomic force microscope, an instrument that is very sensitive to really small forces,” she says. “It lets you get up-close and personal with bacteria.”

She attaches a single cell or molecule to the tip of a probe on the atomic force microscope. Separately, she prepares a test surface – anything from a simulation of the human gut to material from industrial machinery. When she maneuvers the probe close to the surface, the microscope reveals the precise power and nature of the forces that cause the object to stick.

“It’s a puzzle with two key variables – the surface of the bacteria itself, and the surface it adheres to,” Sullan says. “We study hard surfaces versus soft. Charged and non-charged. Polar and non-polar. It gives us fundamental mechanistic insights.”

Sullan, who only recently joined U of T Scarborough's faculty as an assistant professor, has an established career history with small-scale attraction.

“I was already interested in these forces before I came here,” she says. “As a grad student, I studied the nano-forces of barnacle adhesives. My research has practical uses, but I just find it personally fascinating how a single bacterium decides to attach to a surface.”

Understanding one germ might not seem immediately useful. But bacteria rarely act alone. Out in the world, when a single bacterium attaches to a surface, more tend to follow. They create elaborate adhesion structures, and eventually form a complex “biofilm” that covers the entire surface.

Bad things can happen when bacteria get organized in this way.

Biofilms cover medical instruments in hospitals, putting patients at risk of infection risks. They eat away at plastic and rubber parts of aircraft fueling systems through a process called microbial induced corrosion. They even coat human teeth and cause decay – dental plaque is a form of biofilm.

Biofilms involve complicated interactions among millions of bacteria, the adhesive molecules they produce, and the surface itself. But Sullan believes that understanding the basic physical mechanisms governing single cells can help address the larger issues.

“When we know how this works at the nanoscale level, then we know how to interfere with it,” says Sullan. “The insights we’re getting should provide design principles for ‘anti-fouling’ coatings that would repel biological colonization. They could be used for medical implants, as well as in industry, dentistry or elsewhere.”

Conversely, her research might also lead to new types of adhesive based on the gluey molecules some bacteria produce.

Sullan, though, remains focused on the basic research.

“My background and technique are tailored for looking that initial stage when the single bacteria first attaches,” she says. “I believe it’s a crucial stage to study.”

© University of Toronto Scarborough