MBMB 528
July 23, 2004
Content Area : Biology or Lab Sciences (9th Ð 12th)
Objectives:
Students
should be able to develop an understanding of four factors that affect life at
a microscopic level.
Students
should use information about life factors to design an investigation to explore
the growth necessities of a certain organism.
Illinois Learning
Standards:
11.A Know and apply the concepts, principles and
processes of scientific inquiry.
12.B Know and apply concepts that describe how living
things interact with each other and with their environment.
13.A.4b Assess the validity of scientific data
by analyzing the results, sample set, sample size, similar previous
experimentation, possible misrepresentation of data presented and potential
sources of error.
Teacher Directed
Activities:
1. Introduce the lesson with a class discussion on what
is required to live. Show class some petri dishes with growth, and ask what is
necessary for the growth.
2. Discuss and give lecture notes on four factors that
influence microbial growth,
(temperature,
oxygen, pH, osmotic pressure) SEE
BELOW
3. Give various examples of specific species living in
the human body affected by the growth factors. Use pictures when available.
4. Lead students into a discussion of how to test the
optimal growth requirements of a designated bacterium.
5. Oversee their investigations for proper aseptic
technique and ask questions
throughout the process to make sure
students draw connections.
Student Directed
Activities:
1. Students will be given a pre-test to establish current
knowledge base and prepare
for
lesson. SEE
BELOW
2. Students will participate in discussion and take notes
over the lecture material.
They
will be allowed to share examples of various infections they might have
experienced
or have questions about.
3. Given a variety of materials and a few precautionary
guidelines, students will design
a
laboratory investigation to test the optimal growth conditions for a certain
bacterial
species. They should report this to the teacher for approval.
4. Upon approval, students will set up their experiments
and record materials and
procedures.
Then, after several days of growth, they will record their data.
Materials Provided for
Student Investigation:
8 broth tubes
4 agar plates (each with a
different salt concentration)
4 agar plates (each with a
different pH concentration)
Culture of E.coli
Hot plate
Ice
Incubator at 37 degrees
Celsius
Assessment of Learning:
1. Students will be given a pre-test examining knowledge
of growth factors.
2. StudentÕs inquiry skills will be assessed with a
checklist during their experiment
design
and performance.
3. Students will be asked to assess the validity of their
experiment and the results,
closely
examining their aseptic technique and experimental design.
4. Finally, students will be given a post-test about the
content of environmental
factors
affecting microbial growth and about their lab results. SEE BELOW
Notes or Comments:
Time to complete: 3 complete
blocks (70 minutes) spread out over a week so organisms have time to grow. One
day for discussion and experiment design, one day for laboratory
set-up, one day for
laboratory results and assessment.
DISCLAIMER:
This lesson is to be used
only after students have a solid understanding and experience with aseptic
technique. They should already know what is unsafe in working with
microorganisms. Also, the students will have had experiences in designing their
own laboratory activities, before this particular challenge.
A.
Temperature
of environment
Enzymes reactions double for every 10 degree rise in temp.,
but can also be denatured.
1.
psychrophiles
(-5 Ð 20 C)
2.
mesophiles (20 Ð 50 C) Ð most disease-causing
bacteria
3.
thermophiles
(50 Ð 80 C)
4.
extreme
thermophiles(above 80C)
B.
Amount
of oxygenÑmany metabolic processes require oxygen as an electron acceptor.
1.
Obligate
aerobes Ð must have O
Ex. Bacillus
2.
Obligate
anerobesÑcanÕt grow in
presence of oxygen.
Ex. Clostridium botulinim
3.
Facultative
anerobes Ð will use O if available, but can also grown anaerobically.
Ex. E. coli
4.
Microaerophilic
organisms Ð require small amounts of O, but high concentrations are toxic.
Ex. Helicobacter pylori
5.
Aerotolerant
organisms Ð grow in presence or absence of O, but get no benefit from O
Ex. Streptococcus pyrogenes
C.
pHÑmeasure
of the amount of acidic ions vs. basic ions.
Scale of 1-14
1.
most
grow at pH of 7 (neutral)
2.
acidophilic
(acid-loving)
Ex. Helicobacter pylori
D.
Osmotic
Pressure Ð pressure is required for water to flow in & out of the cell.
1.
salt
usually inhibits growth
2. high amounts of sugar also slow growth.
Please
put your answer in the blank to the left.
____ 1. Which of the following factors would
most affect where a
microorganism grows in a broth tube?
a.
temperature b.
pH level
c.
amount of salt d.
oxygen tolerance
____ 2. Which temperature would most
disease-causing bacteria prefer?
a.
temp. of a warm bath b.
temp. of human body
c.
temp. of a feverish person d. melting temp.
____ 3. At which pH would most microorganisms
prefer to live?
a.
slightly acidic b.
slightly basic
c.
neutral d.
strongly basic
____ 4. Which of the following seasonings
would inhibit growth of bacteria and
is thus used as a food preserver?
a.
salt b.
flour c.
yeast d.
baking soda
____ 5. Which of the following is not
necessarily required for some bacteria to
live?
a.
food b.
water c.
oxygen d. nutrients
____ 6. Which part of a cell is most likely to
be damaged by excessive heat?
a.
fats b.
DNA c.
carbohydrates d.
proteins
____ 7. Which of the following would you
expect to affect osmotic pressure?
a.
DNA b.
fats c.
salts d.
proteins
____ 8. The ÒthermoÓ prefix refers to which of
the following words?
a.
salt b.
heat c.
water d.
pH
____ 9. The ÒaeroÓ prefix refers to which of
the following words?
a.
temperature b.
carbon dioxide c. water d. oxygen
____ 10. Substances with a pH less than 7 are
considered?
a.
neutral b. acidic c. basic
Please put your answer in the
blank to the left.
____ 1. Which of the following best describes the amount of oxygen
needed
by E.coli to live?
a. obligate aerobe b.
obligate anaerobe
c. facultative
anaerobe d.
microaerophilic
____ 2. Most disease-causing organisms temperature preference is
described
as
a. psychrophiles b.
mesophiles
c. thermophiles d.
extreme thermophiles
____ 3. An organism that likes acidic environments would probably
live in
the
a. intestines b.
kidneys c.
stomach d.
mouth
_____4. Organisms that grow
in the bottom of a broth tube are probably
a. obligate
anaerobes b.
obligate aerobes
c. psychophilic d.
acidophilic
_____ 5. Which body structure would have the lowest temperature?
a. stomach b.
heart c.
fingertips d.
mouth
____ 6. Which of the following factors would most affect where a
microorganism
grows in a broth tube?
a. temperature b.
pH level
c. amount of salt d.
oxygen tolerance
____ 7. Which temperature would most disease-causing bacteria
prefer?
a. temp. of a warm
bath b.
temp. of human body
c. temp. of a feverish person d. melting temp.
____ 8. At which pH would most microorganisms prefer to live?
a. slightly acidic b.
slightly basic
c. neutral d.
strongly basic
____ 9. Which of the following seasonings would inhibit growth of
bacteria
and is thus used as a food preserver?
a. salt b.
flour c.
yeast d.
baking soda
____ 10. Which of the following is not necessarily required for
some
bacteria
to live?
a. food b.
water c.
oxygen d. nutrients
____ 11. Which part of a cell is most likely to be damaged by
excessive
heat?
a. fats b.
DNA c.
carbohydrates d.
proteins
____ 12. Which of the following would you expect to affect osmotic
pressure?
a. DNA b. fats c.
salts d.
proteins
____ 13. The ÒthermoÓ prefix refers to which of the following
words?
a. salt b.
heat c.
water d.
pH
____ 14. The ÒaeroÓ prefix refers to which of the following words?
a. temperature b. carbon
dioxide c. water d. oxygen
____ 15. Substances with a pH less than 7 are considered?
a. neutral b. acidic c. basic