Into the TC Hood

Though I haven't had deep experience with tissue culture, it is a very important part of our experimental setup. To culture the embryonic stem cells, we use hoods. A hood is a sterile area that with an overhead and side covering that has all the materials tissue culture requires. One of the most important aspects of the hood is it's laminar air flow. To make sure that no contamination is being pushed into the hood, there is a circular air flow that brings air from the back to the front of the hood and back again.

Cells are brought directly from the incubator into the TC hood and the scientists checks if they are "happy". Happy cells are very proliferative, spreading quickly across the bottom of the well, with very few dead cells. The cells media (a solution that is deposited on top of the cells and contains all the molecules it needs to survive) can also tell us about the state of the cells. The media contains an indicator called phenol red that turns yellow as the pH decreases. When the cells undergo glycolysis (their main method of producing energy because they are in an anaerobic environment) they create lactic acid that lowers the pH. So when the media has turned a yellowish color, we know that it contains a lot of waste product (lactic acid) and therefore has mostly been used up. If the cells look unhappy or the media is yellow, the scientist has to change the media. To change the media scientists use a small vacuum to suck the current media out of the well, and replace it with fresh media. They are then transferred back into the warm incubator so the cells can continue to grow.

Recently, we had a problem with our hood. The vacuum that sucks up the media is connected to a jar that is supposed to collect the waste media and supposed to have 10% bleach to kill any cells that might still be alive. Every so often, however, the jar gets full and needs to be emptied out. However, as I discussed in nerd society, all scientists share supplies; therefore, a classic example of the "tragedy of the commons" occurred. Because everyone used the hood, nobody felt personally responsible for it, and nobody emptied out the vacuum jar. In addition, the jar was set up improperly and there was not enough bleach in the jar. The end result was that bacteria began to grow in the jar, and the jar's liquid level filled up until it hit the filter that separated the jar from the rest of the vacuum, and bacteria started growing through the vacuum, contaminating the wells of whoever used the vacuum. Many plates of cells died or had to be purified, and it was a very sad few days at the lab. Our experiments too, were contaminated and will have to be repeated. RIP cell, rest in peace.