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

Choose the option that shows the correct pairing of the products with their corresponding microorganisms.

 
P. Citric acid i. Micromonospora purpurea
Q. Polyhydroxyalkonates ii. Zymomonas mobilis
R. Gentamycin iii. Aspergillus niger
S. Ethanol iv. Ralstonia eutropha

  1. P - i, Q - ii, R - iii, S - iv

  2. P - ii, Q - iii, R - i, S - iv

  3. P - iii, Q - iv, R - i, S - ii

  4. P - iii, Q - i, R - iv, S - ii

  5. P - iv, Q - ii, R - iii, S - i
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Citric acid is obtained from Aspergillus niger. Polyhydroxyalkonates are obtained from Ralstonia eutropha. Gentamycin is obtained from Micromonospora purpurea. Ethanol is obtained from Zymomonas mobilis.

Multiple choice

Azotobacter is

  1. phosphate solubilising bacteria

  2. symbiotic bacteria

  3. non-symbiotic bacteria

  4. gram positive bacteria
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Azotobacter is non-symbiotic bacteria.

Multiple choice

Bacteria having siderophores act as

  1. biofertilisers

  2. iron-chelation agents

  3. Both 1 and 2

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

Bacteria having siderophores act as both biofertilisers and iron-chelation agents.

Multiple choice

SOS repair for repairing mutation errors is used by which of the following?

  1. Pseudomonas aeruginosa

  2. E. coli

  3. Mycobacterium tuberculosis

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

The process by which E. coli repairs large amount of damage is called SOS repair. This process is not a single discrete mechanism. It involves a large number of responses. The ability to repair pyrimidine dimers, to shut off respiration, to delay septum formation and to induce prophages are a few examples. All the processes are well-coordinated.

Multiple choice

Which of the following events takes place in triparental mating?

  1. Two donor cells conjugate simultaneously with a host cell.

  2. One bacterial strain assists another in transferring genetic material to a third bacterial strain.

  3. Host cell receives the genetic material from three donor cells.

  4. Integrated plasmid, along with an external DNA, fuses with the host DNA.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Triparental mating is a form of bacterial conjugation where a conjugative plasmid present in one bacterial strain assists the transfer of a mobilisable plasmid present in a second bacterial strain into a third bacterial strain. In other words, one bacterial strain helps the another in transferring genetic material to a third bacterial strain.

Multiple choice

An example of free living nitrogen fixing aerobic bacteria is

  1. clostridium

  2. rhizobium

  3. azotobacter

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

Azotobacter is a free-living, aerobic, nitrogen-fixing bacteria found in soil. Unlike Rhizobium which forms symbiotic associations with legume roots, or Clostridium which is anaerobic, Azotobacter lives independently and fixes atmospheric nitrogen aerobically. Rhodospirillum is a photosynthetic bacteria, not primarily known for free nitrogen fixation.