1. The preservation of agar slopes has an expiration of 6 months and the agar needs to be changed every 6 months. Which of the following can be used to extent sub-culturing to 1 year?
a) Paraffin oil
b) DMSO
c) Glycerol
d) Loamy Soil
Explanation: The agar slants can be covered by paraffin oil and the extension time can be increased from 6 months to 1 year. DMSO, Glycerol, Loamy soil are used in the preservation techniques for the preservation of microbes more than decades.
2. What is the temperature of liquid nitrogen (°C)?
a) -150°C
b) -122°C
c) -194°C
d) -196°C
Explanation: The temperature of liquid nitrogen is -196°C. It is used to store and preserve the microbial culture for a decade or even more. The cryoprotectants are added to the culture suspension before adding to liquid nitrogen.
3. Which of the following is NOT a cryoprotective agent?
a) DMSO
b) Glycerol
c) Ethylene Glycol
d) Paraffin wax
Explanation: The cryoprotective agents like DMSO, 10% Glycerol, Glycol are the agents that are added to microbial cell culture to protect the cells at a lower temperature or in liquid nitrogen at -196°C.
4. The preservation by liquid Nitrogen is called as ___________
a) Cryopreservation
b) Lyophilization
c) Freeze-drying
d) Desiccation
Explanation: The preservation by liquid Nitrogen is called as Cryopreservation. The cryoprotective agents are added to the culture before preservation, hence the name, Cryopreservation.
5. Which of the following method involves sublimation of cell water?
a) Cryopreservation
b) Lyophilization
c) Dried Culture
d) Desiccation
Explanation: Lyophilization is the method that is based on freezing of culture followed by drying under vacuum. This is known as sublimation. It is useful for the storage or preservation of culture for more about 25 years.
6. “Each batch of newly preserved cultures should be routinely checked to ensure their quality”. Who outlined the statement?
a) Lincoln
b) Snell
c) Malik
d) Pridham
Explanation: Lincoln in 1960 outlined the statement “Each batch of newly preserved cultures should be routinely checked to ensure their quality” for quality control of preserved stock cultures.
7. Which of the following is/are used in dried culture preservation?
a) Sand
b) Soil
c) Sand and Soil
d) Slits
Explanation: The use of sand and soil in dried culture preservation is that it reduces the metabolic activity of the culture and also doesn’t allow oxygen to diffuse.
8. The cultures grown on agar slopes may be stored in the refrigerator or freezer at 5°C to -20°C.
a) true
b) false
Explanation: The cultures grown on agar slopes may be stored in the refrigerator or freezer at 5°C to -20°C and sub-cultured at approximately 6-monthly intervals.
9. Which of the following is NOT the advantage of lyophilization?
a) Dissolution of product
b) Processed in aseptic conditions
c) Handling and processing time increases
d) Do not use heat
Explanation: The processing and the handling time in lyophilization are more as there are many incubation periods, thus a time-consuming process. Handling and processing time is a major disadvantage of lyophilization.
10. The cryoprotective agents are used to prevent cell damage.
a) true
b) false
Explanation: The main function of cryoprotective agents is to prevent cell damage for the preservation of microbial cell culture in liquid nitrogen at -196°C.