Knowing the concentration of microorganisms in a sample is often an important consideration for environmental, industrial, and medical microbiologists, yet a microscope is sometimes not used to accomplish this task

Question

Explain five major limitations to using a light microscope to directly count microorganisms.
What will be an ideal response?

Answer 1

Answer: All of the following eight are potential issues associated with the direct counting method: 1) live and dead cells are indistinguishable without special staining, 2) low cell concentrations are challenging to enumerate, 3) motile cells must be immobilized, 4) precision can be quite poor with manually counting hundreds or thousands of cells, 5) small cells are difficult to observe and count even at 1,000X total magnification, 6) small particulates can be mistaken for microbial cells, 7) unstained cells requires more sophisticated microscopy, and 8) very time-consuming.