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

The basic and first choice of taxonomists for the classification of bacteria is

  1. National Collection of Type Culture

  2. Bergey's Manual of Systematic Bacteriology

  3. International Collection of Microorganisms from Plants

  4. American Type Culture Collection

  5. International Code of Nomenclature of Bacteria
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bergey's Manual of Systematic Bacteriology is known as Bible of bacterial taxonomy. Bacterial taxa, which have been correctly described, are reviewed in Bergey's Manual of Systematic Bacteriology, which aims to aid in the identification of species and is considered the highest authority.

Multiple choice

Which of the following statements are correct with reference to the action of bacteria?

A. Ammonifying bacteria release ammonia in the soil by decay and putrefaction. B. Nitrifying bacteria convert ammonia to nitrates directly. C. Nitrogen fixing bacteria can be symbiotic or non-symbiotic. D. Acetobacter aceti helps in the production of acetone. E. Mycoderma aceti converts sugar solution to acetic acid.

  1. A, C and E

  2. Only A and C

  3. B, C and D

  4. Only D and E

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

Ammonifying bacteria release ammonia in the soil by decay and putrefaction. Nitrogen fixing bacteria can be symbiotic or non-symbiotic. Mycoderma aceti converts sugar solution to acetic acid.

Multiple choice

What is ammonotelism?

  1. Fixing of atmospheric nitrogen by soil bacteria

  2. Elimination of nitrogenous waste in the form of ammonia

  3. Production of ammonia or ammonium compounds in the decomposition of organic matter, especially through the action of bacteria

  4. Elimination of nitrogen in the form of urea
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The process of excretion of nitrogenous waste in the form of ammonia is called ammonotelism.

Multiple choice

Biofertilisers are organisms that enrich the nutrient quality of the soil. Which of the following microbes are used as biofertilisers?

  1. Bacteria

  2. Cyanobacteria

  3. Algae

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

Yes, it is the correct answer. All of these microorganisms (bacteria, algae, etc) are considered beneficial for agriculture and are used as biofertilisers. Fungus also plays a considerable role in the decomposition of organic materials and enrichment of compost.

Multiple choice

Bio-fertilizers such as Rhizobium, Azotobacter, Azospirilium and blue green algae have been in use since a long time. Which among the following is used as a booster for paddy crop grown both under upland and low-land conditions?

  1. Pseudomonas putida

  2. Azospirillum

  3. Anabaena

  4. Nostoc

  5. Azotobacter
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nostoc can fix atmospheric nitrogen and are used as inoculations for paddy crop grown both under upland and low-land conditions.

Multiple choice

Pili are found in

  1. all bacteria

  2. gram +ve bacteria

  3. gram -ve bacteria

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

Pili are commonly found in Gram -ve bacteria. Pili project from the surfaces of some groups of bacteria, these thread like structures help bacteria adhere to one another during mating as well as to animal cells for protection and food.

Multiple choice

The function of leghemoglobin in root nodules in rizobium legume 'symbiosis' is to

  1. protect nitrogenase in nodule bacterium

  2. transport of CO2 to nodule bacterium

  3. give purple colour to nodule bacterium

  4. give N2 to nodule bacterium
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Leghemoglobin binds oxygen with very high affinity, maintaining extremely low free oxygen concentration in root nodules. This protects oxygen-sensitive nitrogenase enzyme from being inactivated by O2. It does not transport CO2, provide color, or supply N2 to the bacterium.

Multiple choice

Which of the following statements is/are true about microbes?

  1. Some microbes are used in sewage treatment processes.

  2. Some microbes are used as food for humans.

  3. Some microorganisms utilise carbon dioxide.

  4. Some microbes provide nitrogen for plant growth.

  5. All of the above

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

Yes, all of the above options are true for microbes.

Multiple choice

Sulphur bacteria are:

  1. heterotrophs

  2. autotrophs

  3. chemoautotrophs

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sulphur bacteria are chemoautotrophs because they oxidize inorganic sulfur compounds (like hydrogen sulfide) to obtain energy for synthesizing their organic food. They don't rely on sunlight (photoautotrophs) or consume organic matter (heterotrophs). Option C correctly classifies them.