Tuesday, March 9, 2010

Shaking (and grinding)

One of the cool devices we have in the lab is our incubated plate shaker. The job of this device is to shake plates while maintaining constant temperature for fast growth (30C in the case of yeast). During this growth the yeast has to be shaken for two reasons. First, to aerate the media which maintain a constant environment (releasing ethanol from fermentation and mixing in oxygen), and second, since yeast tend to precipitate (settle down) in media, it has to be resuspended to ensure that all cells are exposed to similar microenvironment.

As we are using dense formats (96 and 384 well microtiter plates), we need to shake the plates at a high frequency and a small orbit, which usually is not achieved by standard shakers. Since we bought a dedicated shaker, it was a nice bonus that it has its own built-in incubation environment.

Yesterday Ayelet inoculted plates with samples from a library that we got from Ollie Rando's lab. Since there were multiple plates, she stacked them up in two levels. The plates are molded so that the top plate is anchored to the lid of the plate below, and thus does not fall off during the shaking. However, we discovered a curious fact this morning. The plates were dirty with a fine white powder.

Turns out that the high frequency shaking motion was slowly grinding the plates against each other, resulting in this plastic dust. While the grinding does not seem to wear down the edge of the plate in a significant manner, it does create unpleasant source of potential contamination. We need to see whether to stop using two-levels of plates, or figure a way to buffer the grinding.

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