MICR*3430 Microbiological Methods REVIEW QUESTIONS – examples March 27, 2013
1. For isolating DNA, you were asked to have a “fresh, pure culture” ready.
(a) How do you know you have this?
(b) Why is it important?
2. Define and explain the difference between magnification and resolution in microscopy.
3. What determines the differences in resolution in light microscopy and electron microscopy?
4. What are the characteristics of a good research hypothesis?
4a. Give an example of a good research hypothesis, based on an experiment that could
be conducted in the MICR*3430 laboratory. Explain why it is a good hypothesis.
5. The Gram-stain has long been a key primary test for bacterial identification. Why?
5a. Many lab reports said something like: “Gram-stain was determined by KOH method”.
What does that mean? Explain the basis and use of this rapid test.
6. Describe and explain* three different approaches that were used in the laboratory to
determine microbial numbers in samples (e.g. of soil, water). What was the reason or
advantage for using each approach?
*Note: “Describe and explain” is asking you to name the process, with an indication of how it is done and also
comment on the basis for doing it (i.e. why does it work; what makes it appropriate for a particular kind of sample)
7. Compare and contrast the bacterial cell structures that can be seen by light microscopy and
by electron microscopy. (In commenting on the structures seen by electron microscopy,
indicate what kind of electron microscopy.)
8. When we isolate bacteria, probably the first thing we do is look at the colonies that appear on
the plates of agar medium. Why might the appearance of colonies differ for different
bacterial isolates? What kinds of features might you look for?
9. “Actinomycetes” are common soil bacteria and we isolate them on “Actinomycete agar”. Write
a brief description of the group we mean when we say “actinomycetes”. Include
comments about their colonies and the composition of media we use to isolate them.
10. When asked for an example of a selective medium, microbiologists tend to say – quickly-
“MacConkey’s” or “EMB”. Give two examples of media that are selective for microbial
groups that are not Enterobacteriaceae ( E. coli & friends) and explain how the media act
selectively. (HINT: Think – as used this semester?)
11. A laboratory that has worked for many years with strains of E. coli and Salmonella has
decided it is time to meet the rest of the microbial world. They have acquired a vast
diversity of cultures representing different bacterial phyla, and asked you, as a
microbiologist, to advise them on the best way to manage their new culture collection.
What information and advice would you give them? (OK, besides “Hire Me!”) 12. The Genus Bacillus was first described and named by Cohn in 1872,