Tiny creatures, big surprises

“One of the things we found is that when a biofilm grows out, it’s actually strong enough to exert force on the substrate," Patteson continues. "We typically think of biofilms as really slow-growing things, but if they’re on something soft, they can actually disrupt it.” This has implications for disease; it means that tissue damage during and following infection might not just be caused by reactions of the body’s immune system, but from the bacteria exerting strain on it.

Besides design and manipulation of the gels, Patteson and Asp apply physics to biology in the ways that they process the images, measure the boundaries of the biofilms, and calculate how quickly the boundaries expand. “We study mechanics and soft matter systems, so we have equations that describe how something deforms under certain amounts of stress,” says Patteson. Unlike with the less controllable agar, Patteson’s team can now make calculations to measure the forces that the biofilms are putting on the gels. Indeed, by mapping the stress, the team was able to show how biofilms exert more pressure on a stiff surface than on a softer one. “It makes sense, in a way,” says Patteson, “if you tried to climb a sticky wall instead of a slippery wall, you could exert more force on it. We don’t exactly know why in the case of the biofilms, but it makes sense that they’re able to exert more force and move faster.”

“Bacterial organisms, by biomass, are the most predominant life form on the earth,” says Patteson, acknowledging this overlap in interest with Welch, from whose lab they procured the strains of bacteria. “We’re motivated to study them because they intersect with the human world,” says Asp. “Biofilms will grow and be very sturdy, sometimes in places that we don’t want them, whether that’s in patients with disease that are immunocompromised, or in water treatment plants, or on the hulls of ships.”

Looking ahead

It's easy to sense the team’s respect for these microscopic organisms as they speak—indeed, Patteson suggests that they might hold a key to understanding much more about organisms big and small. “We spent 10, 20 years sequencing the human genome, but that’s not enough for us to understand how the body works,” she says. “Just because we know the genome, we still can’t predict how things will behave. This is where soft matter and physics can enter in. And there are a lot of tools for understanding that we have just begun to utilize.”