Students should understand that while staining procedures increase the contrast of cells against the background to make them more visible, they also kill cells and often distort their appearance Discuss phase-contrast microscopy and dark-field microscopy (Figure 2.5), two tools that allow one to look at living cells without the need for staining.This deficiency will lead to a discussion of various methods employed to increase contrast Discuss the various simple dyes used to stain cells, most of which are positively charged, basic dyes capable of binding to negatively charged cell surfaces (e.g., methylene blue and crystal violet Figure 2.3) Continue the discussion of differential stains, the most widely used of which is the Gram stain (Figure 2.4).
Discuss the basic principles and components of the compound light microscope, including the relationships between resolution and magnification, and numerical aperture (Figure 2.1) Note that although bright-field microscopy is fine for visualizing pigmented cells (Figure 2.2), it is not an efficient tool for viewing unstained cells with no natural pigmentation, such as nonphototrophic bacteria.CHAPTER Microbial Cell Structure and Function Summary Chapter is an excellent introductory overview of microscopic techniques and the structure and function of both prokaryotic and eukaryotic cells For courses designed for nonscience majors, this chapter provides general details on each topic that, if supplemented with material from related chapters later in the text, may be sufficient background for most students However, it is recommended that Chapter be used to set the stage for more detailed coverage later in the course 2.1–2.4 | Microscopy The variety of microscopic methods available for observing microorganisms must be introduced early, as much of the presentation of structure–function relationships depends upon the excellent micrographs that appear throughout the book Although details of microscopy are more easily introduced in the laboratory portion of the course, the material included here is pertinent to effective lecture presentation
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