The laser used to 3D print the cages is so precise that it was previously used to make this microscopic chimpanzee skull. Photo: Jason Shear
The most important zoos of the future might not house endangered lions or tigers. Instead, they could hold disease-causing bacteria.
Scientists at the University of Texas have begun 3D printing microscopic habitats to study bacterial communities. They say the tiny "cages" are better at reproducing the microbial environments of the human lungs and gut than traditional petri dishes.
Using a high-precision laser and a protein, the researchers continually print two-dimensional images onto a layer of gelatin where bacteria are being cultivated. As they add more protein layers, the 2D images slowly build up, creating an impenetrable "cage" that the bacteria are confined in. The technology was described in Monday's Proceedings of the National Academy of Sciences.
"We do another layer, and another, and so on, building up," said Jason Shear, one of the researchers working on the project. "It's very simple. We're basically making pictures and stacking them up into 3-D structures, but with incredible control. Think about the thickness of a hair on your head, and take 1 percent of that, and then take about a quarter of that. That's about the size of our laser when it's brought to its smallest point."
The process allows the researchers to control which bacteria live within any one cage. They're also able to control densities, which let them set up conditions that are nearly identical to the colonies that exist within humans.
That's important, because recent discoveries suggest that bacterial arrangements and shapes can play important roles in causing disease.
"To gain detailed insights into how geometry may inﬂuence pathogenicity, we describe a strategy for 3D printing bacterial communities in which physically distinct but chemically interactive populations of deﬁned size, shape, and density can be organized into essentially any arrangement," the researchers write.
In practice, they're studying Staphylococcus auras, a bacteria that can cause skin infections and often develops antibiotic resistance. In cystic fibrosis patients, the bacteria interacts with another type of bacteria, Pseudomonas aeruginosa, which somehow seems to confer antibiotic resistance to the staph bacteria.
"What the technology allows us to do is put them in conversation with each other, in very precise ways, and see what happens," Shear said. "In this case the Staph sensed the Pseudomonas, and one result was that it became more resistant to the antibiotics."
Jodi Connell, another researcher on the project, says that the technology allows scientists to set up a kind of bacterial cage match, if you will.
"It allows us to basically define every variable," she said. "We can also much more precisely simulate the kinds of complex bacterial ecologies that exist in actual infections, where there typically aren't just one but multiple species of bacteria interacting with each other."