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

The smallest bacterium is

  1. Spirillum

  2. Bacillus

  3. Dialister

  4. Both (1) and (2)

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dialister pneumosintes is the smallest bacterium (0.15—0.3 n long). 

Multiple choice

In biogas plant, which group of bacteria is found?

  1. Cyanobacteria

  2. Myxobacteria

  3. Mycobacteria

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

Biogas plants rely on methanogenic archaebacteria (archaea) to convert organic matter into methane-rich biogas through anaerobic digestion. Cyanobacteria are photosynthetic, myxobacteria are soil bacteria, and mycobacteria include pathogens like TB - none are involved in biogas production.

Multiple choice

Rhizosphere microflora exhibits:

  1. Parasitism

  2. Symbiosis

  3. Commensalism

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

The rhizosphere is the narrow region of soil directly influenced by root secretions and associated soil microorganisms. These microorganisms have symbiotic relationships with plants - they help in nutrient absorption, nitrogen fixation, and plant growth promotion in exchange for root exudates as food.

Multiple choice

Nitrogen can only be used after it is fixed. Which of the following can fix nitrogen?

a. Soil microorganisms and associated plant roots b. Lightning and cosmic radiation c. Some marine animals d. Green plants

  1. a and b

  2. a, b and c

  3. a, b, c and d

  4. a, b and d

  5. b, c and d
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct asnwer as soil microorganisms and associated plant roots, lightning and cosmic radiation and some marine animals can fix nitrogen from the atmosphere.

Multiple choice

Which of the following statements is/are correct?

a. Carbon is an essential constituent of different organic compounds, such as amino acids, nucleic acids, proteins, vitamins and pigments. b. Only a few types of organisms, like certain species of soil bacteria and blue green algae, are capable of utilising carbon directly in its gaseous form. c. Carbohydrates that are decomposed by microorganisms, then get oxidised into carbon dioxide and are returned to the atmosphere.

  1. a only

  2. b only

  3. c only

  4. a and b

  5. a, b and c
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is the correct answer as this statement is correct.