By Hillel Aron
By Joseph Tsidulko
By Patrick Range McDonald
By David Futch
By Hillel Aron
By Dennis Romero
By Jill Stewart
By Dennis Romero
Compared to molecules, cells are a good deal easier to observe. When listening to yeast cells, there's no need for an STM — for this essentially biological work Gimzewski can make do with an off-the-shelf atomic-force microscope. It's the AFM that relays the cellular song, channeling the cytological a cappella into the realm of human consciousness. As with an STM, an AFM works by feeling its way over a surface, only here the instrument measures force rather than current. At the end of a cantilevered arm is a microfine tip that hovers above an object like a highly sensitive record needle and picks up minute deviations in topography. Andrew Pelling is the young man in charge of this instrument; Gimzewski has assigned him the cell project as the basis of his doctoral thesis in physical chemistry. He is going to be the first person in the world with a Ph.D. in cell sonics. Small and nervous with dark, dancing eyes, Pelling giggles like a delighted child. And why not? At 24, he is being handed the helm of a ship heading for a new scientific continent, and in the process he may be contributing to a medical revolution.
Separated from the labyrinthine STMs, the AFM is in a room by itself where it can be carefully shielded from external interference. It's placed inside a special foil-lined enclosure to protect the apparatus from electromagnetic fields, and the whole thing is pneumatically suspended on a bed of air to insulate against sound and jitter. When Pelling is running experiments, the hood is closed, the lights are off, everyone is out of the room, and the door is closed. "It's probably overkill," he says. "But we get far better resolution than the manufacturer."
I'm eager to hear a yeast song, and Pelling produces a small test tube of urine-colored liquid with a sediment of whitish sludge congealed at the bottom. "It smells like bread," he says, opening the cap, and when I take a whiff, the aroma of a bakery fills my nostrils, reminding me that through our olfactory sense we humans still maintain a visceral connection to the chemical realm. Pelling takes a pipette and sucks out some of the sludge, then smears it onto a microscope slide.
A typical yeast cell is around 5,000 nanometers (or five microns) in diameter, 10 times smaller than the width of a human hair and well within the range of the AFM. Once the sample is dried, Pelling puts the slide under the scope and closes the hood. We go out to the main lab to watch the creation of the image on a computer monitor. Slowly a mass of cells appears on the screen, small indistinct black and white blobs. Pelling zooms in, and the screen fills with about a dozen cells. At this range they are crammed together, butting up against one another and forcing themselves into a hexagonal pattern. Some are sporting pretty circular protrusions, like microscopic ringworms. "Bud scars," Pelling explains, are the places where daughter cells have budded off from the mother cell, leaving a trace of their cellular birth. He zooms in farther to the middle of a single cell, which appears to be covered with elephant skin.
Pelling locks off the AFM's position and begins to record the up-and-down movement of the tip. This tiny motion of the cell membrane is stored as a digital file to be played back later through a speaker. Because of the extremely low amplitude of the motion, it's not possible to record sound directly. Nor can we hear recordings live, though Pelling is planning to connect up a mixer and some speakers so that he can pipe his minimalist symphonies to the lab at large.
In the meantime, he turns on another computer and pulls up the file of a previous recording. The background noise is especially intense and I strain to hear something coherent. For a moment, I feel like a SETI researcher desperately searching the skies for signs of intelligent life. But as I listen I become aware that amid the high-pitched buzz is a faint rhythmic clicking. The monitor displays the spectral analysis of the signal, revealing a strong, sharp spike at around 1,000 hertz. When Gimzewski and Pelling first captured this signal, they couldn't believe what they were hearing. As Gimzewski notes, "It didn't seem possible that a cell could be vibrating this fast." They had expected that if there was any movement at all, it would be much slower. Initially, they thought the high-pitched spike must be an artifact of their experimental setup; the proof that it's a real signal emanating from the cell is that when they listen to a dead cell, the spike disappears. Pelling plays me the file of a dead cell, and it's pure, flat, monotonous noise.
Next he juxtaposes two different varieties of yeast, one from a naturally occurring strain and another from a genetically modified mutant. Each has a slightly different sound, and the differences between them can be empirically gauged by the variations in their spectral analysis, what physicists call their Fourier transform. Even to the untrained ear, they each have their own unique call. It's weirdly unsettling, listening to the songs of these microbial creatures. Voice is something that seems such a quintessentially intelligent characteristic. The discovery of whale songs, for example, irrevocably altered our view of a species that had until then been largely regarded as an aqueous reservoir of rare oils, while dolphins' clicking has earned them a status in our sentimental landscape that is equaled only by the higher primates. When we hear other creatures "calling," we instinctively begin to imagine an interspecies dialogue. And that is effectively what Gimzewski and Pelling are aiming toward.