Working for the State of Colorado as an environmental microbiologist, your job i

Question

Working for the State of Colorado as an environmental microbiologist, your job is to monitor protozoa populations. New to the job, you collect a water sample from Cherry Creek Reservoir, one of your monitoring sites, and place some of the water on a slide to put under a standard light microscope. In looking at your water sample under the microscope, you quickly get frustrated because you cannot see anything.

(i) Knowing that protozoa are present in the water sample you put under your light microscope, why might you not be able to see anything?

(ii) Remembering your microbiology, you fix the problem and can now see cells under the microscope. What did you do to fix the microscopy problem? However, you recall from your microbiology class that protozoa are motile, but none of the cells under the microscope are moving. You therefore make the conclusion that there are no viable protozoa in the water sample. Is this conclusion correct, why or why not? Base your answer on what you did that allowed you to visualize the protozoa under the microscope.

If Leeuwenhoek had staining available, would his microscope have been able to reach the magnifications seen with light microscopes used today? Explain why or why not.

Explanation / Answer

For visualisation of protozoan, we need some dye for visualisation otherwise it will be transparent. The cells are there certainly but without any dye we can't see them.

In the second step we can heat fix the cells on slide and after it stain them with appropriate dye. This will help in staining the cells and hence visualisation.

Staining can aid in visualisation but it can't increase the magnification. So it wouldn't have helped.

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