Bacteria have a reputation for being little loners, but they often team up to form biofilms—highly organized structures with channels that allow nutrients to enter and waste to exit. These biofilms play a role in many bacterial invasions, including those associated with cystic fibrosis, infections of the urinary tract and middle ear, and the colonization of contact lenses, artificial heart valves and joint prostheses. And they often resist antibiotics.
Now UC San Diego physicists have fabricated a device, consisting of microscopic rooms and hallways to give researchers the opportunity to determine how bacteria organize themselves during the early stages of colony formation. The team from UCSD, Johns Hopkins University, Virginia Polytechnic Institute and Sweden’s University of Lund reported their findings in Public Library of Science Biology, and their research may lead to better ways to treat or prevent persistent infections.
“The device we constructed consists of a series of microscopic chambers machined in a piece of silicone rubber,” explains Alex Groisman, an assistant professor of physics at UCSD, whose team designed and fabricated the microchamber device. “The chambers are so shallow that bacteria align themselves just one cell deep. This is the first time it has been possible to study monolayers of bacteria over many generations under controlled conditions.”
Like partygoers spreading from room to room, the bacteria spread into successive chambers as their numbers increased. However, unlike human revelers, the bacteria became progressively more ordered, aligning themselves with their long axes in the direction toward the nearest chamber exit. This facilitated the escape of cells from the crowded chambers and was also conducive to an increased in-flow of nutrients and out-flow of waste. Therefore, the bacteria organized themselves to make the best of the environmental conditions.
“The device we developed provides a nice platform for studies of the responses of bacterial colonies to drugs, at a single-cell resolution,” says Groisman. “We can look at
different stages of crowding in the microchambers to see how crowding affects resistance to drugs.”
— Sherry Seethaler
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