1. Enrichment media allows the growth of a large number of varied bacterial species.
a) True
b) False
Explanation: Enrichment media is a selective method used for the enhancement of the growth of a particular bacterial species.
2. Which of the following is not a physical method for selection of pure culture?
a) Heat treatment
b) pH of the media
c) Cell size and motility
d) Use of dilute media
Explanation: Use of dilute media is a chemical method of selection in which a mixed culture was inoculated into a very dilute medium to isolate a particular bacterial colony.
3. In physical method of selection, endospore-forming bacteria can be obtained by heating the mixed culture to _____________
a) 70 degree C for 10 minutes
b) 80 degree C for 10 minutes
c) 60 degree C for 10 minutes
d) 90 degree C for 10 minutes
Explanation: To select for endospore-forming bacteria, a mixed culture can be heated to 80 degrees C for 10 minutes before being used to inoculate culture media. Vegetative cells will be killed by this treatment but endospores will survive and subsequently germinate and grow.
4. Vibrio cholerae can grow in a medium with a pH of _______
a) 5.5
b) 7.0
c) 8.5
d) 2.0
Explanation: Vibrio cholerae, cholera causing bacterium can be selected from a medium with a ph of 8.5; most intestinal bacteria are unable to grow at this pH.
5. Disease-producing species occurring in a mixed culture can be selected by taking advantage of _________
a) its pathogenic properties
b) special carbon source
c) special nitrogen source
d) toxic chemicals
Explanation: In the biological method of selection, a disease producing species occurring in a mixed culture can often be selected by taking advantage of its pathogenic properties. Others are chemical methods of selection.
6. A large cluster of colonies are obtained in streak plate method
a) True
b) False
Explanation: In streak plate method, the bacterial cells are thinned out so that the bacterial cells are far apart in the medium to ensure that colony developing from one cell does not merge with that growing from another.
7. Treponema sp. can be selected by taking advantage of ____________
a) small cell size
b) motility
c) dilute media
d) small cell diameter and bacterial motility
Explanation: Treponema sp. from the human oral cavity can be selected by taking advantage of its small diameter and bacterial motility. They have the ability to swim through solid agar media
8. Roll-tube technique is used to isolate ___________
a) aerobes
b) anaerobes
c) facultatives
d) stringent anaerobes
Explanation: Roll-tube technique which is a modification of streak-plate technique is used to isolate stringent anaerobes.
9. In pour-plate method, the medium should be maintained at what temperature?
a) 37 degree C
b) 67 degree C
c) 45 degree C
d) 0 degree C
Explanation: In pour plate method, the medium is maintained in a liquid state at a temperature of 45 degrees C to allow thorough distribution of inoculum
10. Which of the following method can be used to determine the number of bacteria quantitatively?
a) Streak-plate
b) Spread-plate
c) Pour plate
d) Pour-plate and spread plate
Explanation: Due to a higher degree of dilution, pour-plate and spread-plate techniques may be performed in a quantitative manner to determine the number of bacteria present in a specimen.