Which of the following bacteria reduce nitrate in soil into nitrogen?

1. Nitrobacter

2. Thiobacillus

3. Nitrococcus

4. Nitrosomonas

The common nitrogen-fixer in paddy fields is

(1) Frankia

(2) Rhizobium

(3) Azospirillum

(4) Oscillatoria

Azolla has a symbiotic relationship with
1. Chlorella
2. Anabaena
3. Nostoc
4. Tolypothrix

A free living aerobic soil bacterium capable of
fixing nitrogen is
1. Azotobacter

2. Clostridium

3. Rhizobium

4. Streptococcus

During biological nitrogen fixation, the cells of which of the following regions take part in the formation of nodules in roots for bacteroides?
1. Epidermis
2. Cortex
3. Endodermis
4. Vascular bundle

Thiobacillus is a group of bacteria helpful in carrying out:

1. Denitrification

2. Nitrogen fixation

3. Chemoautotrophic fixation

4. Nitrification

A plant requires magnesium (Mg) for:

1. holding cells together

2. protein synthesis

3. chlorophyll synthesis

4. cell wall development

Which of the following is responsible for biological nitrogen fixation?

1. Nif gene

2. Nitrogenase

3. Both 1. and 2.

4. RNA synthetase

Which of the following is a non-symbiotic nitrogen fixer organism?

1. VAM

2. Azotobacter

3. Anabaena

4. Rhizobium

Azotobacter and Bacillus polymyxa are

1. Decomposers

2. Nonsymbiotic nitrogen fixer

3. Symbiotic nitrogen fixer

4. Pathogenic bacteria