Yeast Lab: the sound of microbes & magnetic fleas

Last week I had a wonderful day with Simon Park, recording the sounds of the microbiological laboratory at Surrey University. Simon, an expert in microbiological luminescence, had very kindly set up a number of cultures: a conical jar of yeast and two petri dishes of other luminescent microbe colonies. The cultures are kept in a series of incubator rooms set to different temperatures in order to aid the growth of microbes. The room set to human body temperature is breathtakingly warm; I had no idea that I was this hot.

This initial visit to the lab was a kind of acoustic reconnaissance: lets listen to what is there to hear. Simon showed me the various machines used to stir and agitate the liquid cultures. This includes the ‘Magnetic Flea’, a seemingly uninteresting, elongated plastic covered magnet, visually not unlike a suppository. However, when the flea is put into a jar placed on a spinning machine, it begins an untidy clangorous choreography, as it rattles against the glass walls of its container. Finding equilibrium, it produces a distinct pattern of movement and sound, each magnet composing its own percussive stir: unique to that jar, that flea, in that moment and that position. The patterns continually evolve and change like listening to waves fall onto the shore, a sonic equivalent to the visual patterns of growth produced by the microbes in the petri dish.

We spent hours (and I do mean hours) trying different jars, different fleas, different microphones, and different spinners. Some of the machines allow the speed of stir to be varied, so that the jars can be ‘played’ like a musical instrument. And whilst some machines spin to stir, others have a gentler shaking action, like the clichéd motion supposedly used to swill brandy around the bottom of a glass.  I recorded many variations of instruments, jars and microphones to capture a canon of growing percussive patterns.

In one of the incubator rooms I placed contact microphones against the sides of a conical jar containing yeast. On the surface of the solution you could see small eruptions of gas as the yeast feeds, digests and expels. In appearance it is not unlike looking through a telescope at the surface of some gaseous planet. It is interesting that visually we often find the microscopic and macroscopic interchangeable: so what would be the audio equivalent? I suppose the contact microphone may be seen as a form of aural microscope: delving beneath the surface to listen to the very substance of things, bringing the tiniest sound closer and making it available to the ear.

Through the glass membrane of the conical jar, the snap, crackle and pop of yeast digestion is audible, although the contact microphone also picks up the vibration of the incubators heating system  travelling through the metal shelving system. This metallic hum adds a laboratorial ambience to the sound here, (I have reduced it slightly in post-production, so as to emphasise the sound of yeast). The drone of environmental climate control could perhaps be called the ‘keytone’ sound of the laboratory (and of the archive; a soundscape I have also explored). R Murray Schafer described a Keynote sound as ‘often not consciously perceived’ but ‘heard continuously or frequently enough to form a background against which other sounds are perceived.’ In the laboratory the hum of temperature control pronounces an acoustic stasis, the pulsing sound of time standing still.

A hydrophone sunk into the solution, is surrounded by the digestion of yeast, although again the ambient sound of the laboratory is also present in the mix: this time it’s the voices of people preparing to experiment. In order to get a larger hydrophone in on the action, we decant the yeast to a metal pan and notice (through the microscope of contact microphones) a change in the acoustics resulting from the metal skin of the pan. Another experiment, set-up quickly by Simon, involved two conical jars and a rubber tube. By gently stirring one jar full of yeast, the gas escapes up the tube into a jar full of water, producing quite delicious bubbles of effluent.

The yeast songs have their own pattern, as the microbes consume all available oxygen and food, the static crackle of their existence is extinguished. There is the possibility of producing a spatial and acoustic bell curve, through which could be heard the life cycle of these microbes, their multiplication, peak and extinction: a microbiological soundscape, beginning with silence and returning to it.

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3 comments
  1. Christopher Little said:

    Lovely text, interesting soundscape, fascinating ideas.

    • Thank you Christopher. Hopefully Simon and I will be expanding upon this idea. So new sounds are promised.

  2. Shingo Modulation said:

    nice sound and nice photos!

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