Note: This lab report is turned in after you have
viewed the slides for both the spore stain and the capsule stain (sometimes the
capsule stain is done as a demonstration but you are responsible for looking at
a capsule stain slide and knowing how it is done and important to
remember, we are using the nigrosin stain procedure as described in Ex. 3-5
[negative stain] to stain for capsule!).
Also, this lab has 2 parts which might be done on 2 separate days. When
turning in the lab, make sure you include BOTH
parts. It is turned in after the capsule stain part is completed. (Note: Our lab manual claims endospore has keratin. It
is actually a protein that is keratin-like.)
Bacterium for the spore stain
is: Bacillus subtilis. Bacteria for capsule stain are Enterobacter
aerogenes & S. aureus.
Q1.What
is the function of a bacterial endospore? Hint: How easy is an endospore to destroy? Use
your textbook/lecture notes to help you.
Q2.
Why does this exercise call for use of an older culture of Bacillus? What does a positive result for a spore stain
indicate about the organism? What does a negative result for the spore stain
indicate about the microorganism?
Q3.
List three specific functions
of capsules. Use your textbook/lecture notes to help you. (Hint: two of these
functions are often listed as functions of various virulence factors). Note: It is not enough to say that it protects
bacteria from the immune system or that it is a virulence factor.
Q4.
In the capsule stain process used in class (using nigrosin), are the bacterial
cells heat-fixed to the slide? Why or why not?
Q5.
Eosin is an acidic red stain and methylene blue is a basic blue dye. What should be the result of staining a smear
of encapsulated bacteria with a mixture of eosin and methylene blue?
Please
note if the capsule is stained or not stained at all.
For
lab exam: you should have a general idea regarding: the bacterial spore cycle
(its different stages).
As
a somewhat related question to Q1, is endospore formation a form of bacterial
reproduction or is it doing something else for the bacteria? Explain your
answer. Also you should understand why
an acidic stain such as nigrosin or eosin, which in many cases is being used
for a negative stain procedure, does not colorize the cells in a bacterial
smear.
As
mentioned in lab, how does India ink work as a negative stain (as compared to
nigrosin).
Last Completed Projects
| topic title | academic level | Writer | delivered |
|---|