A nitrogen-fixing microbe associated with Azolla in rice field is

• Spirulina

• Anabaena

• Frankia

• Frankia

Which one of the following is an example of carrying out biological control of pests/diseases using microbes?

• Trichoderma sp. against certain plant pathgens

• Nucleopolyhedrovirus against white rust in Brassica

• Bt-cotton to increase cotton yield

• Bt-cotton to increase cotton yield

What gases are produced in anaerobic sludge digesters?

• Methane and CO₂ only

• Methane hydrogen sulphide and CO₂

• Methane, hydrogen sulphide and O₂

• Methane, hydrogen sulphide and O₂

In gobar gas, the maximum amount is that of

• butane

• methane

• propane

• propane

Where do certain symbiotic microorganisms normally occur in human body?

• Caecum

• Oral lining and tongue surface

• Vermiform appendix and rectum

• Vermiform appendix and rectum

Consider the following four statements (a–d) and select the option which includes all the correct ones only:
Single cell Spirulina can produce large quantities of food rich in protein, minerals, vitamins etc.
Body weight-wise the microorganism Methylophilus methylotrophus may be able to produce several times more proteins than the cows per day.
Common button mushrooms are a very rich source of vitamin C.
A rice variety has been developed which is very rich in calcium.

• Statements (III), (IV)

• Statements (I), (III) and (IV)

• Statements (II), (III) and (IV)

• Statements (II), (III) and (IV)

Which of the followings is mainly produced by the activity of anaerobic bacteria on sewage?

• Propane

• Mustard gas

• Marsh gas

• Marsh gas

Which of the following helps in absorption of phosphorus from the soil by plants?

• Rhizobium

• Frankia

• Anabaena

• Anabaena

19.

Nitrifying bacteria

• convert free nitrogen to nitrogen compounds

• convert proteins into ammonia

• reduce nitrates to free nitrogen 

• reduce nitrates to free nitrogen 

Secondary sewage treatment is mainly a 

• mechanical process

• chemical process

• biological process

• biological process