Not everyone is musical. Some of us can barely hum in tune let alone perform Beethoven’s ‘Für Elise’ perfectly on the piano. However, we are far more musically talented than our (or more pertinently, other people’s) ears give us credit for. We actually possess ten trillion tiny musical maestros: our cells. These little sacks, busy keeping us alive with their toolbox of biological equipment, have been caught whistling while they work.
The discovery of the cellular symphony was made in 2001 when a UCLA biophysicist, Jim Gimzeweski, wondered whether the vibrations emitted by certain cells as they grow and divide could be interpreted as audible sound. Along with his graduate student Andrew Pelling, he attempted to investigate these potential noises using a highly sensitive microscopic needle, which gently touched the cell membrane and read any movement and vibration created by a cell – much like the needle on a record player (Figure 1). The recorded movement was relayed to a computer which calculated the frequency, pitch and volume of each vibration to convert it into a discernible note, amplified loud enough for humans to hear.
This first foray into the study of cell sounds, known as ‘sonocytology’, began with yeast: a cell that pulsates around a thousand times a second. When the needle first touched a quivering yeast cell, an eerie hum was released into the room, which was music to Jim’s ears. “Beautiful” was how he described these unexpected ‘good vibrations’. Fascinated, the pair questioned whether changes in a cell’s environment or physiology would alter their acoustical ability. When they dropped the cells into ethanol, that pleasant hum morphed into a high-pitched wail as the cells unleashed a deafening screech right before they perished. Once the cells were dead, only a feeble hissing sound escaped them – as if deflating and exhaling their last breath. Even subtle changes in temperature caused a cell’s vibrations to speed up or slow down, which invariably made them change their tune. And perhaps most interesting of all was that yeast cells with genetic mutations created slightly different sounds to their normal counterparts. The membrane vibrations changed, altering pitch, frequency and volume, each to a unique note depending on the type and number of mutations.
Our cells may not have the X Factor, but their biological babble may have a valuable role. It can provide rare insight into cell health, and if a cell is cancerous, it is obvious to the ears. Biologists Richard Snook and Peter Gardner at the University of Manchester were able to distinguish prostate cancer cells from normal cells simply from the sounds they made. Unlike yeast, human cells do not possess a rigid cell wall; their wobbly membranes produce muffled and intangible sound. However, the pair utilised a technique known as photo-acoustic detection to coerce both the healthy and unhealthy cells into shrieking by exciting them with infrared light. The heat from the laser caused the surrounding air to heat up and cool down rapidly, promoting cellular vibrations which could then be recorded as sound. And the inharmonious racket from the cancer cells would have Simon Cowell enraged. Whilst they recited the same song as the healthy cells, Gardner described the chorus of the cancer cells as “horribly out-of-tune”. Researchers at the University of Missouri-Columbia adopted this same technology to detect skin cancer cells (melanomas) in blood samples. They successfully picked out the cancerous cells by the piercing scream emanating from the cells with excess melanin. Being able to simply ‘hear’ these caterwauling cancer cells prevented the need to conduct painful, and invasive, skin biopsies. The reasons for this vocal disparity are unclear, but cancerous cells possess corrupt internal machinery: they divide uncontrollably and their DNA becomes riddled with mutations. Both of these undoubtedly impact on cell membrane integrity which may consequently modify the rates of vibration, resulting in distinctive noises.
Whilst these approaches require some serious ‘tuning’, the discovery of these scientific concertos may prove a tremendous step forward in medicine. This biological warning siren may allow the sound of an unhealthy cell to become a standard diagnostic tool – catching disease far earlier than a battery of current diagnostic tests ever could. As scientists begin to understand the link between cell sounds and cell behaviour, these tunes could be further used to our advantage. Do certain sounds reflect particular physiological responses? Could we control our cells through the power of music? Maybe playing the cell equivalent of ‘Für Elise’ will encourage a group of cells to grow, multiply and even change their identity, which might facilitate the repair of damaged tissue and organs. It seems that our ten trillion tiny friends have a lot to say for themselves; perhaps it’s time we started listening.
Harvey, T.J. et al (2007). Discrimination of prostate cancer cells by reflection mode FTIR photo-acoustic spectroscopy. Analyst, 132: 292-295.
Pelling, A. et al (2004). Local Nanomechanical Motion of the Cell Wall of Saccharomyces cerevisiae. Science, 305: 1147-1150.
Singing Yeast Cell: http://www.prx.org/piece/976#description
Weight, R.M. et al (2006). Photoacoustic detection of metastatic melanoma cells in the human circulatory system. Optics Letters, 31: 2998-3000.
By Dr. Liam Hurst
Foundation Year 1 Doctor; General Surgery; Norfolk and Norwich Hospital