BIOL-2026EL Study Guide - Final Guide: Saccharomyces Cerevisiae, Staphylococcus Epidermidis, Growth Medium
1 Feb 2021
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Bacterial cells have no colour, even when magnified. They are transparent and do not contrast with their environment. Unless a phase-contrast microscope is used to view them, we must stain the bacteria using dyes (stains) in order to observe them under a microscope. Once they are stained, the appearance, shape, size and arrangement of the cells can be studied. The preparation of a stained smear involves several steps. Bacteria are placed onto a microscope slide in the form of a smear and the slide is then heat fixed to adhere the bacteria to the slide. For a simple stain, the positively-charged dye (basic dye) that is used is attracted to the negatively-charged bacterial cytoplasm. In this exercise, you will learn the detailed steps that are required to prepare a simple stain. Your instructor will demonstrate the techniques required for handling the bacteria (review exercise 2).
