Part 1: Viewing Prepared Slides of Common Bacterial Shapes

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Bacterial Morphology

Part 1: Viewing Prepared Slides of Common Bacterial Shapes

Familiarize yourself with each morphological type to use as a comparative tool for the remainder of the activity. Record your observations.

Part 2: Disinfecting Your Area to Use Live Organisms:

Part 3: Viewing Live Organisms – Wet Mount Preparation

Record your observations.

Part 4: Direct Staining:

Record your observations for each sample.

Part 5: Indirect Staining:

Examine the stained specimens and record your results.

Questions:

A.What are the advantages of using bleach as a disinfectant? The disadvantages? The advantages of using 70% alcohol? The disadvantages? a.An advantage of bleach disinfectant is that is easy and inexpensive, and a disadvantage is that if touches clothing while cleaning if will fade. b.An advantage of alcohol is that it is good in hospital settings for soaking surgical equipment but a disadvantage is that it is not good for wiping down surfaces because it is necessary to have a contact time of 10 minutes with any disinfectant.

B.List three reasons why you might choose to stain a particular slide rather than view it as a wet mount. a.A wet mount, allows one to observe bacteria in terms of their motility and provides some insight on the organism’s overall morphology. However, since the bacterial cell is transparent and motile and therefore somewhat difficult to observe when using the compound brightfield microscope. Bacteria are almost colorless (remember, all cells are composed primarily of water) and therefore show little contrast with the broth in which they are suspended. Bacteria have almost the same refractive index as water. This means when you try to view them using a microscope they appear as faint, gray shapes and are difficult to see. Staining cells makes them easier to see. Staining provides a reliable means for observing bacteria in terms of their relative size, morphology and cellular...
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