Use of a Refrigerator in Microbiology

In microbiology, scientists use refrigerators to create an environment to replicate cells and to perform experiments on a cell to determine how bacteria or other microorganisms affect the cell. The types of cells usually targeted for refrigeration are microorganisms called "mesophiles" and "psychotrophs." Scientists normally have three uses for refrigerating cells: storing the cell for later use; preventing the overgrowth of cells; and reducing the rate of activity on a cell to prevent mutations and additional bacteria microorganisms from appearing.

Things You'll Need

• Petri dish or test tube
• Medium (i.e. sugar)

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Instructions

• 1

  Store cells for later use with refrigeration. Most bacteria are single-cell organisms. If the bacteria reproduce, there will be more cells. A common microorganism that thrives between 25 degrees Celsius (77 degrees F) and 40 degrees Celsius (104 degrees F) is called a mesophile. These microorganisms grow well inside the bodies of warm-blooded animals. Storing them in the refrigerator stops them from multiplying further.

  When growing bacteria on petri dishes, the best practice is to grow isolated colonies. Isolated colonies provide qualitative characteristics that may be used to compare with other colonies growing in the same medium. Colonies are groups of bacteria that have grown from one bacterial cell. For example, "Colony 1" originated from the incubation and growth of "Bacterial Cell 1." Refrigeration keeps the individual colonies from overpopulating and ensuring they remain isolated.

• 2

  Refrigerate cells to prevent overpopulation. The lower temperature slows changes that a microorganism might experience at room temperature, prevents cellular processes from rapidly occurring and slows cell growth and cell death. Refrigeration also inhibits the rate of chemical reactions from occurring that, in turn, slow the growth of other microorganisms called "psychotrophs." Usually growing only at room temperatures, psychotrophs can still grow on refrigerated media, but not in high numbers. Though it is unlikely for psychotrophs to appear on cells in the refrigeration state, scientists check for their presence and whether they will grow despite the refrigeration.

  Refrigeration keeps cells from overpopulation. If cells overpopulate, nutrients in the growth media are depleted. Cells die without nutrients. Too many cells also lead to more toxic wastes. Cells cannot thrive in their own waste.

  A controlled temperature environment also allows you to test how other variables affect cell growth.

• 3

  Suspend cells to low activity or inactive states with refrigeration. Cells may mutate as they divide, so refrigeration prevents changes in the organisms. For instance, some experiments need a certain amount of time with the medium (such as sugar) to determine what the reaction is and what kind of bacteria are produced with the medium. Putting the test tube in the refrigerator after the experiment has run for an allotted time stops further change from occurring. Thus, the results can be recorded.

  Because most bacteria and other microorganisms grow quickly at room temperature, refrigeration allows scientists to monitor the effects of how microorganisms mutate or multiply when combined with different kind of media (i.e. food, sugar). Recording such effects at room temperature would be impossible due to the exponential rate microorganisms grow in an unrefrigerated environment.