Saturday, August 21, 2004

On how microbes interact with their environment... 

The interaction of microorganisms with their environment is critical to much of how we live: this interaction is the determining factor in much disease, it plays a significant role in the stability (or lack thereof) of the climate system and often determines such things as the cleanliness of our groundwater. For many years much of the interaction of microorganisms with their environment has been assumed to be largely chemical and largely atomic. For example the uptake of nutrients and the evacuation of cellular wastes happens usually because of some type of diffision, i.e. the process is explicable purely by paying attention to the relevant molecules.

Andrew E. Pelling, Sadaf Sehati, Edith B. Gralla, Joan S. Valentine, and James K. Gimzewski, in a just published paper in the journal Science, have found that the cell walls of live yeast cells vibrate with a characteristic frequency which is dependent on temperature. They argue that these oscillations are likely driven the the passage of groups of motor proteins on the inner side of the cell wall - something like the vibration of a house's wall as a nearby frieght train roles past (as Gimzewski explains on his web site). For the technically inclined, I should note that Pelling performed the observations using an AFM (atomic force microscope - essentially a molecularly small record needle) and live cells caught in the pores of a polycarbonate filter).

While the actual observation is interesting, even more interesting are the consequences. Pelling et al. seem to make the case the in the paper (and Gimzewski makes the case in other articles about the research) that it is likely that the observed oscillations are somehow passive: that they are diagnostic of healthy cell function. But it's clear from the paper that the oscillations take a lot of energy. It seems at least possible to me that, if the oscillations truly served no useful purpose (for the cell) the energy used to create them would have long ago been channelled elsewhere more effectively.

If the oscillations actually serve a purpose, it's not at all clear what that might be. More work is needed with tools which say something about the chemistry happening at the same time as these observed mechanical changes and that can resolve the dynamics of these chemical changes.

So there's still a long way to go, but if this oscillatory behaviour turns out to be spread widely among microorganisms, and if it turns out to be useful (to the cell) Pelling et al. have opened the door to an interesting new world.

The reference for the paper (only accessible over the web if you have a subscription to Science) is,

Pelling et al., Local Nanomechanical Motion of the Cell Wall of Saccharomyces cerevisiae, Science 2004 305: 1147-1150

However, if you'd like a reprint and don't have a subscription you can drop Gimzewski a line and ask him for one here.

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