LAB REPORT 6- Selected
questions from Exercise 5-10, 5-11, and 5-13 ( extracellular enzymes)
(In your results, do not
just say positive or negative reaction for the 3 different bacteria on the 4
different media. Explain the color / media changes that are occurring and explain what is happening
biochemically. You are responsible for knowing about the theory behind all
4 media as well as the results of all 4, unless told otherwise.)
Bacteria
being used in these exercises will include: Bacillus subtilis, E. coli, S.
aureus, S. epidermidis, and potentially Serratia marcescens. In class you will get further instructions.
Q1.
What is the role of extracellular enzymes in bacterial metabolism?
Q2.Suppose
you had poured iodine on your plate and noticed clearings in the uninoculated
area, as well as around both of your transferred cultures? What are some
possible explanations for this occurrence?
Was the integrity of the exercise compromised? What kinds of things might be done to avoid
this problem in the future?
Q3.Is
it acceptable to read a positive test before the incubation time is completed
for an assay such as the milk plate assay?
Why is this not the case in a starch agar assay? How about an early negative result?
Q4.Why
is it advisable to use a positive control along with organisms that you are
testing?
Note:
For lab exam: i) what does the enzyme
casease (a type of protease) have in common with amylase ii)how do you know
these are exoenzymes rather than working in the cytoplasm iii) besides the term
depolymerization (disassembly of DNA), what other term can be used to describe
this process
iv)With
respect to the Starch Agar assay, how would you expect the results to change if
you were to add glucose to the medium (in addition to the starch already
present)? V) How might the results obtained in these exercises be used for the
identification and/or classification of bacteria?
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