Transcript Marks/markah - Portal UniMAP

1. Microorganisms require about 10 elements in
large quantities for the synthesis of
macromolecules. State clearly all the
elements.
[10 marks]
2. Describe energy and carbon requirements
each of the following group of
microorganisms.
a) Photoautotrophs
b) Chemoautotrophs
c) Photoheterotrophs
d) Chemoheterotrophs
[20 marks]
3. Different species of microorganisms can grow
in a wide range of environments and their
growth rates are influenced by physical and
biochemical factors.
i. Lists four physical factors that affect
microbial growth.
[5 marks]
ii. Define the term ‘acidophiles’ and
‘alkaliphiles’ and name one common genus
from each group.
[20 marks]
4) Initial information obtained for bacteria found in
contaminated milk is that they belonged to
photoheterotrophs group. The milk was pasteurized
at 72oC and then cultured on nutrient agar media.
The bacteria colonies appeared after three days.
i. What are the assumptions that can be made for their
carbon and energy sources?
ii. Explain the appearance of colonies and suggest the
bacteria group based on the physical requirements.
[20 Marks/markah]
5) Information on bacterial growth is very important in food
and industrial microbiology.
i. Draw and label a typical bacterial growth curve and
describe the phases involved.
[15 marks]
ii. Fifty cells of a bacterial species with a generation time of
25 minutes are introduced into a fresh sterile medium at
9.00 AM. The culture is maintained at an optimum
growth temperature throughout the experimental
period. Calculate the number of bacterial cells that can
be obtained in this experiment at 3.00 PM and the
number of generations by 6.00 PM.
[10 marks]
6) An inoculum of 107 bacterial cells was
introduced into a flask of culture medium and
the
growth was monitored. No change
was observed for the first 18 minutes; then
growth occurred rapidly. After a further 76
minutes, the population had increased to 4.32
× 108
cells. Calculate the doubling time (Td)
of the culture?
[20 marks/markah]