Example Answers to Bacterial Smear and Simple Stain Questions PDF

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lab micro 234 example homework questions and answers...

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Bacterial Smear Questions 1.

Is a coverslip used with a bacterial smear? No. No coverslip is used when making a bacterial smear.

2.

How much water is needed to make a smear? A single drop of water is required to make a bacterial smear. The time required for air-drying will increase if too much water is used.

3.

Why is a bacterial smear allowed to air-dry prior to heat-fixing? The air-drying step begins the dehydration process that serves to protect the shape of the cells. If a smear is heat-fixed while water remains, there is a risk of cell lysis.

4.

How much time is required to heat-fix a smear for simple staining? A bacterial smear should be heat-fixed for 20 seconds prior to performing a simple stain.

5.

What is the purpose of the heat-fix step? The heat-fix process serves multiple purposes. The heat fix step fully dehydrates the cells, this preserves their shape on the slide. Heating the smear causes the cells to stick to the glass, and kills pathogens, making the slide safer.

6.

What are the hallmarks of a well-made smear? A well-made smear is made up of a single layer of cells with open space between cells.

Simple Stain Questions 1.

What cellular morphology features are observed after a simple stain? Cell shape and cell arrangement can be determined using a simple stain.

2.

What is the basic difference between a simple stain and a complex stain? Simple stains use a single reagent in a single step, and complex stains use multiple reagents in multiple steps.

3.

What is the proper location for disposal of a bacterial smear after performing a simple stain? After use (simple stain, Gram stain, endospore stain), bacterial smears are disposed of in a 10% bleach solution.

4.

You use crystal violet to make a simple stain. You observe purple cells. Does this indicate that the bacterium is Gram-positive?

No. Regardless of cell type, a cell will take on the color of the reagent used in the simple stain.

Simple Stain Results Questions 1.

What are your observations and conclusions for this correctly performed simple stain? Observation Blue spherical cells, most are in grape-like clusters Conclusion Cells are coccus in shape, possibly staphylococcus

2.

What are your observations and conclusions for this correctly performed simple stain? Observation pink cells, cells are longer than they are wide Conclusion Cells are bacillus in shape

3.

What are your observations and conclusions for this correctly performed smple stain? Observations purple cells longer than they are wide Conclusions Cells are bacilli...