Microbes are present everywhere, including extreme sites like deep inside geysers where the temperature may be as high as:

[Microbes-in-Human-Welfare] [class-xii ]

• 80°C
• 150°C
• 100°C
• 1000°C
Correct Option: C  [ 100°C ]

Remark: Microbes are present even at sites where no other life-form could possibly exist, such as deep inside the geysers (thermal vents) where the temperature may be as high as 100°C.

Which of the following is an example of a proteinaceous infectious agent mentioned among microbes?

[Microbes-in-Human-Welfare] [class-xii ]

• Viroids
• Protozoa
• Prions
• Fungi
Correct Option: C  [ Prions ]

Remark: Microbes are diverse, including protozoa, bacteria, fungi, viruses, viroids, and also prions that are proteinacious infectious agents.

Microbes like bacteria and many fungi can be grown on nutritive media to form visible masses called:

[Microbes-in-Human-Welfare] [class-xii ]

• Suspensions
• Aggregates
• Flocs
• Colonies
Correct Option: D  [ Colonies ]

Remark: Microbes like bacteria and many fungi can be grown on nutritive media to form colonies that can be seen with the naked eyes.

What is the common term used for micro-organisms such as Lactobacillus that convert milk to curd?

[Microbes-in-Human-Welfare] [class-xii ]

• Anaerobic slime
• Methanogens
• Lactic Acid Bacteria (LAB)
• Acetobacter
Correct Option: C  [ Lactic Acid Bacteria (LAB) ]

Remark: Micro-organisms such as Lactobacillus and others are commonly called lactic acid bacteria (LAB) and grow in milk, converting it to curd.

The conversion of milk to curd by LAB improves its nutritional quality primarily by increasing the content of which vitamin?

[Microbes-in-Human-Welfare] [class-xii ]

• Vitamin C
• Vitamin A
• Vitamin B12
• Vitamin D
Correct Option: C  [ Vitamin B12 ]

Remark: LAB convert milk to curd, which also improves its nutritional quality by increasing vitamin B 12.

The puffed-up appearance of dough used for making foods like dosa and idli is primarily due to the production of which gas?

[Microbes-in-Human-Welfare] [class-xii ]

• O2
• H2S
• N2
• CO2
Correct Option: D  [ CO2 gas ]

Remark: The puffed-up appearance of dough is due to the production of CO2 gas during fermentation by bacteria.

Which species of yeast is commonly used for fermenting the dough used for making bread, and is also called baker’s yeast?

[Microbes-in-Human-Welfare] [class-xii ]

• Monascus purpureus
• Saccharomyces cerevisiae
• Trichoderma polysporum
• Propionibacterium sharmanii
Correct Option: B  [ Saccharomyces cerevisiae ]

Remark: The dough for making bread is fermented using baker’s yeast (Saccharomyces cerevisiae).

The traditional drink ‘Toddy’ from southern India is prepared by fermenting the sap from which source?

[Microbes-in-Human-Welfare] [class-xii ]

• Sugar cane
• Rice slurry
• Maize stalks
• Palms
Correct Option: D  [ Palms ]

Remark: ‘Toddy’, a traditional drink of some parts of southern India, is made by fermenting sap from palms.

The large holes characteristic of Swiss cheese are caused by the production of a large amount of CO₂ by the bacterium named:

[Microbes-in-Human-Welfare] [class-xii ]

• Lactobacillus acidophilus
• Propionibacterium sharmanii
• Streptococcus pneumoniae
• Acetobacter aceti
Correct Option: B  [ Propionibacterium sharmanii ]

Remark: The large holes in “Swiss cheese” are due to production of a large amount of CO₂ by a bacterium named Propionibacterium sharmanii.

The large holes characteristic of Swiss cheese are caused by the production of a large amount of CO2 by the bacterium named:

[Microbes-in-Human-Welfare] [class-xii ]

• Lactobacillus acidophilus
• Propionibacterium sharmanii
• Streptococcus pneumoniae
• Acetobacter aceti
Correct Option: B  [ Propionibacterium sharmanii ]

Remark: The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii.