Scientists at The University of Texas at Austin have figured out how to make structures – like houses or cages – that are small enough to corral bacterial cells. The enclosures can be built in any shape and are 3-D printed using a modified laser, the team reported Oct. 7 in Proceedings of the National Academy of Sciences.

Bacteria trapped in a square cage multiply over several hours. (J. Connell et al, PNAS)

But instead of facilitating microbial cage-fighting matches, the microscopic structures should help scientists learn how infections spread and how bacteria talk with one another – a complex process involved in everything from population regulation to toxin release to the development of drug resistance.

To cage cells, scientists first select a microbe to work with. For example, they may use Staphylococcus aureus, which causes skin infections and can mutate into the antibiotic-resistant superbug known as MRSA. Next, they suspend the bacteria in a warm, gelatin-based solution that contains light-sensitive molecules. Then they cool the mixture, which solidifies into a Jell-O like substance and traps bacteria where they are.

Six cultures of P. aeruginosa (green) are trapped inside spherical cages (red). In the side view, the tops of the cages have been digitally removed to reveal the bacterial clusters. (J. Connell et al, PNAS).

Now, the scientists select which cells to cage, and trigger the light-sensitive molecules embedded in the matrix. Shining the laser at the trembling mass activates these photosensitive proteins, which snap together and form solid bonds. Moving the laser lets the team build cages of any shape and nearly any size. The traps have pores that are big enough for nutrients and signaling molecules to squeeze through, but small enough to keep the bacterial cells inside.

In this way, the team can create zoo-like enclosures around individual cells, or mini gated communities of microbes. They can feed the different communities different nutrients, or cut the communities from the gelatin and move them closer to or farther from their neighbors – kind of like gerrymandering congressional districts, but less nefarious in purpose and on a smaller scale. They can reorganize entire communities, and embed clusters of cells within other species.

When the team looked at how communities of S. aureus acquired drug resistance, they found that the bacteria were more impervious to antibiotics when surrounded by a different microbe, called Pseudomonas aeruginosa. Thus, though physically separated, the two microbes had worked together to combat introduced antibiotics.