Nikhil Bhatla, a Postdoc in the Horvitz Lab at MIT, recently discovered that worms can spit. He and his team used high-speed recordings to examine what happened when they exposed eating worms to light, which gen- erates toxic hydrogen peroxide. They learned that the worm’s pharynx—or mouth—contains neural circuits that
can detect if something it is eating is toxic. If so, the worm spits the food out.
This work began when Bhatla was a student and the find holds implications for the human heart that could change
the way valvular heart disease is treated. Bhatla recently spoke to LabOutlook about his work and discovery.
Q:Why did you choose C. elegans as a model?
A: When I started grad school, I wanted to understand the neural mech- anisms of consciousness by doing experiments with visual perception
in monkeys. But as I learned just how complex mammalian brains are, and
just how difficult it is to rigorously study mammalian neural circuits, I decided to search for a simpler organism. I read a wonderful study on the neural
network control of touch avoidance by leeches, but unfortunately (or fortunately) no one at MIT studies leeches. Instead, a fellow grad student told
me about a lab in the Biology department that studied one of the simplest
nervous systems that we know of, that of the roundworm C. elegans.
C. elegans is a wonderful model of more complex animals because it
contains all the same kinds of cells as other animals, but they are reduced
in number. The C. elegans nervous system consists of only 302 neurons,
compared to an estimated 86 billion neurons in the human brain. The feeding behavior that I study is a behavior of the pharynx, which serves as the
worm’s mouth and pumps food into its gut.
The pharynx itself in some ways resembles the human heart, as both
organs fundamentally function as biological pumps. The pharynx also has
its own intrinsic nervous system, which
consists of even fewer neurons, only 20.
This limited number meant that I could do a comprehensive analysis of the
neural control of feeding by systematically killing each neuron individually
and observing the effect, if any, on feeding behavior. So, with the worm, I
was able to rigorously and comprehensively analyze the neural control of an
Q:How did you identify the neurons that control food intake in C. ele- gans?
A: To gain insight into the neural circuits that control feeding by the worm, I took advantage of the fact that the C. elegans feeding organ,
the pharynx, contains only 20 neurons in 14 classes. Since the worm is
transparent, I could visualize each neuron under the microscope and shine
a laser directly targeting each one. The laser has such high energy that it
causes the water in the neuron to heat up, burning and killing the neuron.
But, the laser is so precisely focused that nearby cells are completely unaf-
fected, so laser microsurgery truly is the most precise kind of surgery.
One by one, I killed each class of neurons in the pharynx, and checked to
IN THE SPOTLIGHT
Scientist in the Spotlight: How Spitting
Worms Can Help the Heart