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Life Science

  • Introduction to Sterile Technique In this lab, students practice transfer of a bacterial culture using sterile technique. View »
  • Introduction to Prokaryotes: Bacteria What are bacteria? In this introductory lab students make smears of bacteria on microscope slides from pure cultures, perform a simple stain, and observe their stained slides under a microscope View »
  • Bacterial Growth on MacConkey Agar In this lab students culture three bacteria on nutrient agar and MacConkey agar and record the results. View »
  • Introduction to Prokaryotes: Archaea In this lab, students are introduced to Halobacterium, a representative of the Archaea, one of the three domains of life (along with Bacteria and Eukarya). View »
  • Isolating Bacteria from a Mixture How does a microbiologist isolate bacteria from a sample? In this lab students practice streaking a plate to isolate a single species of bacterium from a known mixture. View »
  • Bacteria: The Indole Test In this lab students perform a differential test to distinguish bacteria based on the production of indole. Bacteria are grown on media containing tryptophan and then treated with Kovac’s reagent. If they possess the enzyme tryptophanase, the bacteria can metabolize tryptophan into indole, pyruvic acid, and ammonia. View »
  • Decomposition by Physarum polycephalum Observe the phenomenon of the plasmodial form of Physarum polycephalum as it streams in search of a food source. Essential question: What role do decomposers play in an ecosystem? View »
  • Bacterial Hydrolysis of Casein In this lab, students culture two bacteria on skim milk agar. The protein casein gives milk its white color. Some bacteria secrete protease enzymes that can hydrolyze casein. When these bacteria are grown on skim milk agar a clear area develops around the colonies, indicating that casein has been hydrolyzed into its component amino acids. View »
  • Bacterial Hydrolysis of Starch In this lab, students culture two bacteria on potato dextrose agar, which contains starch. When grown on potato dextrose agar, bacteria that can secrete amylase—an enzyme that hydrolyzes starch—create a zone around their colonies in which starch is absent. When the agar is flooded with iodine solution, most of the plate stains dark blue–black, but clear areas are left around colonies that secrete amylase. View »
  • Bacterial Motility In this lab, students perform two exercises that investigate microbial motility. One is on a microscopic level, using the “hanging drop” slide preparation method to directly observe motile cells. The second exercise is on a macroscopic level and involves inoculating motility test media. View »
  • Bacterial Hydrolysis of Lipids In this lab, students culture two species of bacteria on agar medium that contains an emulsion of plant oils and the dye, sprit blue, which forms a complex with the triglycerides of the oils and gives an opaque blue color to the agar. Colonies of bacteria that can secrete lipase, an enzyme that hydrolyzes triglycerides, develop a light area or “halo” in the surrounding medium, due to the diffusion of lipase into the medium and the resultant breakdown of the oil/spirit blue complex. View »
  • Bacteria: The Citrate Test In this lab students perform a test on two different bacteria to determine whether the organisms can use citric acid as their sole carbon source. The citrate test is often performed as part of the IMViC (Indole, Methyl Red, Voges-Proskauer, and Citrate) series of tests used to differentiate common species of enteric bacteria. View »
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