When scientists at Berkeley Lab receive samples of malaria parasites, they store them in a freezer until they are needed for study. The parasites can be frozen indefinitely as long as they are frozen in the ring stage. During this stage, they tend to be most resilient to adverse conditions. This is a picture of the liquid nitrogen freezer (dewar) where the malaria samples are stored.

Preparing Malaria Cultures for Study

When the malaria samples are removed from the freezer, they are dormant. To "wake them up," three kinds of salt and sugar solutions are added to them. The solutions help the frozen blood thaw without damaging the fragile red blood cells and the intracellular parasites. In this picture, a researcher thaws out a sample of malaria-infected blood inside a fume hood. He does all the work inside the hood so the samples won't be contaminated by other infectious agents.

Isolating Malaria-Infected Blood Cells

Cultured red blood cells are suspended in a gelatin solution so that researchers can separate the malaria-infected blood cells from the uninfected blood cells. Uninfected blood cells are regularly shaped and have a tendency to stack together in columns upon contact when they are in the gelatin. The infected blood cells are irregularly shaped, so they do not stick to other blood cells. Because the uninfected cells stack up into bigger and heavier clusters, they sink to the bottom of the solution, while the lighter infected cells stay at the top. Thus the cells are separated and the researchers have a purified population of malaria-infected cells.

Expanding the Malaria Culture

The infected cells are kept in an incubator at 37 degrees Celsius (body temperature), the optimal climate for the parasite to flourish. When the temperature drops below this, the malaria parasite's metabolism slows down and its growth is much slower. At body temperature, the parasite can survive indefinitely with daily maintenance. When they are done with the cultures, the researchers centrifuge the sample, remove the excess media, suspend the cells in a freezing solution, and put the malaria back in the freezer until they are needed for the next experiment.