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Training Amoebas

By Erika Engelhaupt
Pablo Iglesias, Tamara O'Connor, Douglas Robinson, Peter Devreotes, and Takanari Inoue all have appointments in the Johns Hopkins School of Medicine.

If you zoomed in very, very closely on the soil under your feet—microscope close—you’d see a teensy-tiny version of the African savanna. It’s teeming with predators and prey locked in a fight for survival, but instead of cheetahs bounding after gazelles, this scene is filled with amoebas chasing down bacteria.

The amoeba Dictyostelium discoideum, affectionately known to scientists as Dicty, is a skilled predator that lives in soil and can chase down its bacterial prey. A team of Johns Hopkins researchers is finding new ways to train this predator to hunt and kill bacteria that cause disease.

It’s a bit like training a dog to herd sheep and fend off the wolves, says Tamara O’Connor, a microbiologist who’s studying how the amoeba detects and kills Legionella bacteria, which can cause Legionnaire’s disease. “We’re training Dictyostelium to seek out and destroy harmful bacteria,” she says, “while leaving the innocuous and beneficial bacteria alone.”

How does one train microscopic predators? That’s where the innovative science comes in. Funded by DARPA, a U.S. research agency that supports basic science with the potential to become groundbreaking technology, the team is taking an engineering approach to biology.

O’Connor is figuring out how the amoeba senses and responds to signals from different bacteria. Pablo Iglesias, a computational biologist, and Peter Devreotes, a cell biologist, are designing special sensors for the amoeba, meaning they’ll outfit it with molecular machinery that helps it decide which bacterial signals to respond to, allowing it to preferentially seek pathogens. Cell biologist Douglas Robinson studies how the amoebas move toward their prey and is trying to figure out how to make the Dicty move fast and become the Usain Bolt of amoebas. Synthetic biologist Takanari Inoue will work on linking these biological components together.

“The immediate goal is to combine a synthetic system in a living cell and have them prefer the pathogenic bacteria—go after it and engulf it,” Robinson says.

While it’s amazing to imagine the possibilities of an army of amoebas prowling a hospital corridor in search of infectious bacteria, the team is quick to say they won’t be releasing amoebas into the environment. “We need to be responsible and not create new problems,” O’Connor says.

They do hope, though, that someday disease-fighting amoebas can help improve water quality, prevent human exposure to harmful bacteria, or lead to new ways to boost our body’s defenses against harmful bacteria. After all, the way an amoeba hunts down a pathogen is much like the way white blood cells in our immune system do the same thing. “We’re all really just amoebas with hair. Everything we’ve learned about amoebas we have also found in human biology,” Robinson says.

The team is a year into its four-year research, with real-world applications likely a decade or more away. Robinson says it’s worth the wait. As the son of a veterinarian, he grew up seeing animals suffer from genetically inherited illnesses. When he got interested in genetic engineering as a way to fight disease, the technology was in its infancy. He’s excited to put new tools to work. “We’re
willing to play the long game,” he says.

Illustration above by Scott Bakal; Illustration to the left by Wenjia Tang
A team of Johns Hopkins researchers is finding new ways to train the amoeba known as Dicty to hunt down and kill bacteria that cause disease.

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