Biology · Environmental Studies

Microbiology and Nitrogen Cycle

950 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

To select for spontaneously arising histidine auxotrophs in a population, you would use a medium containing

  1. Histidine and penicillin

  2. Penicillin but no histidine

  3. Histidine and lysozyme

  4. Lysozyme but no histidine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Penicillin kills actively growing cells (prototrophs). If you want to select for auxotrophs (which cannot grow without histidine), you provide histidine so they survive, while the prototrophs are killed by penicillin in the absence of histidine (or by using a counter-selection method).

Multiple choice

Which of the following are expected to be the abundant inhabitants of a nitrate and sulfate rich soil naturally depleted for oxygen?

  1. Pseudomonas and Azotobacter

  2. Pseudomonas and Desulfovibrio

  3. Azotobacter and Thiobacillus

  4. Nitrosomonas and Nitrobacter
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In an anaerobic environment rich in nitrate and sulfate, microorganisms capable of anaerobic respiration using these alternative electron acceptors will thrive. Pseudomonas species are well-known denitrifiers, and Desulfovibrio species are classic sulfate-reducing bacteria.

Multiple choice

Based on their properties, match the “Genera” in Group 1 with those in Group 2

Group 1| Group 2| | P. Bacillus| 1. Sarcina| | Q. Neisseria| 2. Azotobacter| | R. Rhizobiurn| 3. Hyphomicrobium| | S. Caulobacter| 4. Clostridium|

  1. P - 4, Q - 1, R - 2, S - 3

  2. P - 4, Q - 1, R - 3, S - 2

  3. P - 2, Q - 4, R - 1, S - 3

  4. P - 1, Q - 4, R - 2, S - 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Bacillus (Clostridium - related), Neisseria (Sarcina - related), Rhizobium (Azotobacter - related), Caulobacter (Hyphomicrobium - related).

Multiple choice botany plant breeding biotechnology for improved food quality plant breeding for food production

Beta-carotene can be induced in the golden rice by a process known as

  1. Biological nitrogen fixation

  2. Biofortification

  3. Bioremediation

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Biofortification is the method in which the food is added or supplemented with the required nutrients. The staple crop like rice is fortified to produce the precursor of vitamin A. Golden rice is the transgenic rice in which beta-carotene synthesizing gene psy and crtl are incorporated by the help of genetic engineering. Beta-carotene is the precursor of the vitamin A. The consumption of the golden rice can help to prevent the deficiency disorders due to less intake of vitamin A. 

Thus, the correct answer is option B. 

Multiple choice biology respiration in living organisms breathing in plants mode of respiration in plants process of respiration

Which one of the following organism may respire in the absence of oxygen?

  1. Azotobacter

  2. Clostridium

  3. Rhizobium

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

Azotobacter is a genus of free-living nitrogen-fixing bacteria that are typically aerobic, but many organisms like Clostridium are obligate anaerobes. However, the question asks which 'may' respire in the absence of oxygen; Clostridium is a classic example of an obligate anaerobe, but Azotobacter is often cited in specific contexts of facultative or microaerophilic capability in curriculum materials.

Multiple choice factors affecting respiration living organisms and energy production life processes in living organisms- part 1 respiration biology

Which one of the following organisms may respire in the absence of oxygen?

  1. Azotobacter

  2. Clostridium

  3. Rhizobium

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

Obligate anaerobic beings are those that cannot survive when oxygen is present. Some fungi, some bacteria (like the agent of botulism -Clostridium botulinum, and the agent of tetanus- Clostridium tetani) and some protozoans are examples of obligate anaerobes.

Multiple choice biology micro - organism useful actions of algae introduction to algae algae

Which type of algae are helpful in nitrogen economy?

  1. Green algae

  2. Blue green algae

  3. Red algae

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

The majority of blue-greens are aerobic photoautotrophs, their life processes require only oxygen, light and inorganic substances. At the onset of nitrogen limitation, during bloom conditions, certain cells in Anabaena evolve into heterocysts, which convert nitrogen gas into ammonium, which is then distributed to the neighboring cells of a filament. In addition, blue-greens that form symbiotic (mutually beneficial) relationships with a wide range of other life forms, can convert nitrogen gas into ammonium.

Therefore, the correct answer is option B.

Multiple choice biology micro - organism useful actions of algae introduction to algae algae

Which of the following blue-green algae helps in the formation of biofertilizers?

  1. Anabaena

  2. Ocillataria

  3. Nostoc

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • All of the above organisms are the genus of cyanobacteria which are used for fixing nitrogen in the nitrogen cycle.
  • So the correct answer is 'All of the above'.
Multiple choice evs atmosphere- wind importance of oxygen is air present everywhere around us? air as a natural resource

Choose the correct answer from the alternatives given.
The largest reservoir of nitrogen on earth is:

  1. soil

  2. oceans

  3. air

  4. granite rocks
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

It is true that 70% or so of the Air is nitrogen but that it needs to be the largest reservoir. Nitrogen is an essential part of most living organisms. Most of the bodily fluids and enzymes have nitrogen in a bonded form. This is true even in the case of plants. So, the correct answer is "Air".

Multiple choice biology reproduction in animals story of dolly, the clone sheep story of dolly, the clone process of cloning

'Nif' gene for nitrogen fixation in cereal crops like wheat, jowar etc., is introduced by cloning.

  1. Rhizobium meliloti

  2. Bacillus thuringiensis

  3. Rhizopus stolonifer

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

Rhizobium meliloti is a nitrogen-fixing bacterium often studied for its nif genes, which are involved in the nitrogen fixation process.

Multiple choice biology air and atmosphere natural cycles and resources constituents of air medicinal use of microorganism component of air - nitrogen

Natural fixation of nitrogen takes place through a non-biological process called ___________.

  1. artificial fixation

  2. nitrogen fixation by lightening

  3. industrial fixation

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

In non biological fixation of nitrogen when the plant dies the fixed nitrogen is released making it available to other plants and this helps to fertilize the soil. The great majority of legumes have this association but a few genera do not. In farming practices fields are rotated through various crops like clover and buckwheat which are known as green manure.