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

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

Mycobacterium is an acid-fast bacteria. It can be stained with

  1. Auramine O

  2. Triarylmethane dyes

  3. Aluminon

  4. Aniline Blue WS
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Auramine O can be used to stain acid-fast bacteria (e.g. Mycobacterium), where it binds to the mycolic acid in its cell wall) in a way similar to Ziehl-Neelsen stain. It can also be used as a fluorescent version of Schiff reagent.

Multiple choice

Bt toxin is produced by B. thuringiensis in inactive form. Which of the following is responsible for the conversion of inactive Bt toxin into its active form?

  1. Acidic pH of the insect gut

  2. Alkaline pH of the insect gut

  3. Action of gut enzymes

  4. The microflora of the gut
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The alkaline digestive tract of the insects denatures the inactive toxin crystals making them soluble and thus, amenable to being cut with proteases found in the insect gut. This liberates the active toxin from the crystal, which then destroys the insect.

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

Bacillus is the name given to

  1. rod-shaped bacterium

  2. spherical-shaped bacterium

  3. comma-shaped bacterium

  4. a virus

  5. star-shaped bacterium
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Bacillus is the name given to rod-shaped bacterium.