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LUMINESCENT BACTERIA Background: There are many different types of microorganisms, and each kind has properties and functions that make them unique. Luminescent bacteria, for example, are unusual because they convert chemical energy into light, which allows them to glow in the dark. Most luminescent bacteria are found in the ocean, and are associated with marine animals like shrimp, clams, or fish. Some fish, such as the flashlight fish, possess a special gland in their body, called the light organ, in which luminescent bacteria can grow. In the flashlight fish, the luminescent bacteria are closely packed in the light organ, and so the fish appears to glow in the dark. Biologists do not yet know why these bacteria produce light. One idea is that producing light gives these bacteria an advantage for survival. By glowing, they attract fish, which they then use as a host organism – the bacteria are able to live in the fish’s body. These fish, which are attracted to the bacteria’s light, pick up the bacteria and prevent them from settling on the bottom of the ocean, where there is less oxygen available. The fish might also benefit from allowing the bacteria to live in their body – the fish are able to glow due to the presence of luminescent bacteria, and this light might help them to spot food more easily in the dark ocean. Today we will streak luminescent bacteria on solid medium (agar plate) so that you will be able to see them grow and glow. Materials: • Plate with luminescent bacteria (Each group will have an agar plate on which luminescent bacteria are growing). • Agar plates (one for each student) • Toothpicks • Parafilm Procedure: 1: Open the lid of the demo plate containing luminescent bacteria. 2: Lift some of the bacteria from that plate with a toothpick. 3: Use the bacteria on your toothpick to write or draw something on your own plate. Be careful not to press too hard so you don’t press through the agar 4: Wrap your plate with parafilm so that it is sealed tightly. 5: Take your plate home and leave it at room temperature for several days. The luminescent bacteria should have grown on your plate after 2 or three days. If you then look at the plate in the dark, you should be able to see the bacteria glowing. You might not be able to see the glowing bacteria right away as your eyes have to adjust to the dark. Questions 1: Can you think of other organisms that are able to produce light? 2: Can you come up with other reasons why it might be advantageous for these bacteria to produce light?