Biology · Environmental Studies

Microbiology and Nitrogen Cycle

1,029 Questions

This hub focuses on microbiology and the nitrogen cycle, covering essential concepts about bacteria and soil microbes. Topics include nitrogen fixation, bacterial structures, and soil microbial processes. These concepts are frequently tested in general science sections of various competitive exams.

Nitrogen fixing bacteriaGram-positive bacteriaBacterial flagellaDenitrifying bacteriaAmmonia conversion processBacterial resting spores

Microbiology and Nitrogen Cycle Questions

Multiple choice

From which of the following organisms are Ti plasmids isolated?

  1. Bacillus thuringiensis

  2. Rhizobium leguminosarum

  3. Agrobacterium tumefaciens

  4. Thermus aquaticus

  5. Escherichia coli
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ti plasmids are isolated from Agrobacterium tumefaciens. Tumor inducing plasmids are double stranded circular DNA present in Agrobacterium tumefaciens.

Multiple choice

Which step of nitrogen cycle is not appreciated by farmers?

  1. Lightning fixes nitrogen as compounds in the soil.

  2. Blue-green algae fix nitrogen as compounds in the soil.

  3. Denitrifying bacteria turn the nitrogen compounds back into gaseous nitrogen.

  4. Ammonia, nitrite, nitrate, etc., remain in the soil.

  5. Presence of rhizobium in root nodules.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This step reduces fertility. Hence, it limits plant growth and causes loss to the farmer.

Multiple choice

Which of the following are blue green bacteria?

  1. Eubacteria

  2. Cynobacteria

  3. Actinobacteria

  4. Archaebacteria
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Blue-green bacteria are correctly called Cyanobacteria. While option B says 'Cynobacteria', this is clearly the intended answer despite the typo. Cyanobacteria are photosynthetic bacteria formerly known as blue-green algae.

Multiple choice

Which of the following bacteria have vacuoles?

  1. Neisseria

  2. Methanococcus

  3. Nitrosomonas

  4. Thioploca
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Thioploca is a genus of filamentous sulfur bacteria, which contain large vacuoles. The cytosol is extremely reduced in this genera and the vacuole can occupy between 40–98% of the cell. The vacuole contains high concentration of nitrate ions.

Multiple choice

Why are certain bacteria called cyanobacteria?

  1. Because they possess cyanide.

  2. Because they possess blue pigment.

  3. Because they possess carbon dioxide.

  4. Because they produce their own food.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Blue-green algae have a blue pigment, i.e. cyanin along with chlorophyll. Thus, they are called cyanobacteria.

Multiple choice

The rod shaped bacteria are called ________.

  1. cocci

  2. bacilli

  3. spirilla

  4. vibrio

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The rod-shaped bacteria are called bacilli, round shaped are called cocci, spiral shaped are called spirilla, and comma-shaped are called vibrious. 

Multiple choice

Which of the following bacteria helps to fix the atmospheric nitrogen in the root nodules of leguminous plants?

  1. Rhizobium

  2. Rhizopus

  3. E.Coli

  4. Mucor
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rhizobium is a nitrogen-fixing bacteria that forms symbiotic relationship with leguminous plants, living in their root nodules and converting atmospheric nitrogen into ammonia that plants can use. Rhizopus is a fungus, E.Coli is a gut bacteria, and Mucor is also a fungus - none of these fix atmospheric nitrogen.

Multiple choice

Nitrogen is a severe chemical in both the protein and DNA. So every living organism should metabolize nitrogen for surviving. Only bacteria and Archaea are capable to convert gaseous nitrogen (N2) to and from soluble ionic compounds, which other organisms may metabolize.

Which of the following bacteria minimizes nitrate to gaseous nitrogen?

  1. Pseudomonas

  2. Azospirillum

  3. Nitrosomonas

  4. Nitrococcus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pseudomonas minimizes nitrate to gaseous nitrate, which is actually denitrification and is a microorganism facilitated method of nitrate reduction that finally produce molecular nitrogen (N2) via sequence of intermediate gaseous nitrogen oxide products. 

Multiple choice

Nitrogen is a severe chemical in both the protein and DNA. So every living organism should metabolize nitrogen for surviving. Only bacteria and Archaea are capable to convert gaseous nitrogen (N2) to and from soluble ionic compounds which other organisms may metabolize.

At the time of symbiotic biological nitrogen fixation, the understanding of Rhizobia host interaction includes 2 types of molecules. Which are they?

  1. Lectin and polysaccharides

  2. Flavonoids and lipids

  3. Lectins and lipids

  4. Lectins and alkaloids
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

These are Lectin and polysaccharides. Lectin has been filtered from seeds of 4 legumes & lectin covalently attach to Agarose. Lipopolysaccharide is isolated from the 4 rhizobial symbionts of legumes. 4 Lipopolysaccharide are passed through 4 lectin columns.

Multiple choice

Which of following are essential properties of prokaryotes (methanogenic bacteria)?

  1. These cannot develop automatically.
  2. Those dwelling in mud supernatant may need organic development factors for development.
  3. These cannot transform hydrogen to methane.
  4. These cannot utilize CO2 as growth substrate in which CO2 is reduced to methane.

Choose the right answer using the options provided below:

  1. 1, 2 and 3

  2. 1, 3 and 4

  3. 1, 2 and 4

  4. 2, 3 and 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Essential properties of prokaryotes (methanogenic bacteria): Those dwelling in mud supernatant may need organic development factors for development. These cannot transform hydrogen to methane & cannot utilize CO2 as growth substrate in which CO2 is reduced to methane.

Multiple choice

Iron uptake is problematic owing to the insolubility of the Fe 3 + ion (usually in the form of hydroxides). Microbes overcome this difficulty by secreting special high-affinity, iron-binding molecules termed as __________.

  1. siderophores

  2. permeases

  3. methionine

  4. vitamins

  5. phosphoenolpyruvate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is true. Microbes have built up specialized transport systems called siderophores. After the molecule is transported in, it gives up the iron ion which is then reduced to the ferrous form (Fe 2+). These siderophores are recycled.

Multiple choice

Whenever bacteria are inoculated into a fresh culture medium, they show characteristic growth curve having four distinct phases. Indicate the phase wherein all the nutrients in the culture medium are used up and the inhibitory end products of metabolism get accumulated.

  1. Lag phase

  2. Log phase

  3. Stationary phase

  4. Death phase

  5. Intermediary phase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

During the stationary phase, the nutrients in the culture medium are used up and the inhibitory end products of metabolism get accumulated.

Multiple choice

Frankia is a genus of the bacterial group termed as actinomycetes. Which of the following is NOT true for this particular genus?

  1. These are filamentous bacteria.

  2. They are noted for the production of airborne pores.

  3. The common soil dwelling streptomyces belong to this group.

  4. They develop nitrogen fixing root nodules.

  5. Frankia species are very fast growing in culture.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The species grows very slowly in culture.