Most of us are familiar and fascinated with ‘big-game’ animals like rhinos, elephants and tigers. Thankfully, they are now protected animals and their numbers have stabilised, but remain perilously low. For instance only around 3,000 tigers remain the in the wild.
By contrast, there are tens of millions of species of bacteria living in the wild. But even these are hard to capture and some are just as elusive as a Siberian Tiger.
Finding ‘wild bacteria’ is a major challenge. And it’s not just their small size that’s a problem. A bit like getting a panda to breed in a zoo, the overwhelming majority of microbes refuse to grow in the laboratory. This is despite decades of scientists’ best efforts to coax the microscopic organisms into action.
Queue the ‘little-game’ hunters like Slava Epstein, a biology professor at Northeastern University, who has dedicated his career to coming up with alternative methods for cultivating bacteria.
His favorite strategy is to take the lab bench into the wild. In nature, bacteria are exposed to a host of nutrients and supportive chemicals that help them grow. But scientists don’t know which ones.
Rather than hunting rifles, Slava uses devices which incorporate permeable membranes that allow sequestered bacteria to be exposed to the nutrients and molecules of their native environment.
But even this approach has limitations. Natural competition between species, even in the wild, has restricted the number of species Epstein can successfully isolate this way. A few years ago he and his collaborator Yoshiteru Aoi at Hiroshima University in Japan began to fantasise about a device that would permit just a single bacterial cell to enter. Once inside, this cell would proliferate as in his other devices, but here it would be free of competition from other species. It would provide a pure sample—just one species.
The answer to this challenge has come from a chemical engineer. Edgar Goluch, DiPietro assistant professor in the Department of Chemical Engineering at Northeastern found the solution.
Ed’s lab is focused on creating microfluidic devices for detecting various biological entities, be it a bacterial cell or an enzymatic molecule. In 2012, he and Epstein teamed up to make a series of prototype devices.
Ed explains his device like this: “Think of a five lane highway going down to one lane. That’s essentially what this does only for bacteria.”
The tiny device consists of an inner chamber containing a food source, to which the only access is a microscopic passageway just slightly narrower than a single cell.
The passageway is so small that the first cell to enter it gets stuck, blocking entry by any other cell or species. The trapped cell is still able to proliferate, however, and when it does it fills up the inner chamber with a pure, single-species sample. Whoever gets there first wins and gets all the stuff inside.
Slava explains how the devices can be used: “We’d like to throw these into any environment on the planet…the deep ocean, under the soil, into a pond… we don’t have to do anything, just build the devices and throw them into the environment. Nature does the rest.”
In order to reach that kind of range, Ed is working with a number of industry partners to streamline and scale the fabrication process.
Slava and his team are already testing the prototypes in Greenland for their first taste of real-world experimentation. And to quote Slava: ““Without Ed…we wouldn’t have been able to do anything.” Sound familiar to all you chemical engineers out there? Good luck with the ‘little-game’ hunting.