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Biology LibreTexts

3: Meet the yeast

  • Page ID
    17509
  • Screen Shot 2019-01-02 at 7.48.26 PM.pngCells and microorganisms are too small to be seen with the naked eye, so biologists use microscopes to see them. In this lab, you will learn to adjust the light microscope using a human blood smear as the specimen. You will then use the microscope to analyze cultures of the budding yeast, Saccharomyces cerevisiae, and the fission yeast, Schizosaccharomyces pombe. Since these two yeast diverged from a common ancestor, they have evolved distinct morphologies and controls on cell division that you will be apparent under the microscope. You will also observe the much smaller bacterium, Escherichia coli, which is one of the workhorses of molecular biology.


    Objectives

    At the end of this laboratory, students will be able to:

    • identify the components of a compound light microscope.

    • describe the types of cells found in a human blood smear.

    • adjust a light microscope to observe bacterial and yeast cultures.

    • stain microbial samples with iodine to improve their optical contrast.

    • distinguish E. coli and yeast by their sizes.

    • distinguish S. cerevisiae and S. pombe by their morphological characteristics.


    Microscopes are essential for viewing cells and microorganisms. Anton van Leeuwenhoek was the first to observe human blood cells and to observe yeast and bacteria, which he referred
    to as animalcules. In this lab, you will use the compound light microscope to observe these same kinds of cells. Yeast are single-celled eukaryotes that are smaller than blood cells, but much larger than prokaryotes, such as Escherichia coli. With the microscope, you will be able to observe
    the divergent properties of the two yeast species we are using in our research, Saccharomyces cerevisiae and Schizosaccharomyces pombe.