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

Which of the following statements is/are correct?

  1. Nitrogen fixation also refers to biological conversions of nitrogen.
  2. Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen (N2) is converted into ammonium sulphate (NH4) by an enzyme called nitrogenase.

  1. Only 1

  2. Only 2

  3. Both of these

  4. Neither of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nitrogen fixation is a process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3). Nitrogen fixation, natural and synthetic, is essential for all forms of life because nitrogen is required to biosynthesize basic building blocks of plants, animals and other life forms, e.g. nucleotides for DNA, RNA and amino acids for proteins. Nitrogen fixation also refers to other biological conversions of nitrogen, such as its conversion to nitrogen dioxide. Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by an enzyme called nitrogenase.

Multiple choice

Which of the following microorganisms can fix nitrogen?

  1. Cyanobacteria
  2. Green sulfur bacteria
  3. Azotobacteraceae
  4. Rhizobia
  5. Frankia

  1. 1 and 4

  2. 1, 3 and 4

  3. 1, 2, 3, 4 and 5

  4. 1, 2, 3 and 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Nitrogen fixation is a process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3). Nitrogen fixation also refers to other biological conversions of nitrogen. Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by an enzyme called nitrogenase. All the given microorganisms can fix atmospheric nitrogen.

Multiple choice

Match the following microorganisms to the processes/products involved:

Column I Column II
W. Pseudomonas putida 1. Bio-insecticides
X. Thiobacillus thiooxidans 2. Bioleaching
Y. Bacillus thuringiensis 3. Bioremediation
Z. Ralstonia eutropha 4. Bio fuels
A. Anabaena 5. Bio fertilizer

  1. W - 4, X - 3, Y - 2, Z - 1, A - 5

  2. W - 4, X - 2, Y - 1, Z - 3, A - 5

  3. W - 3, X - 2, Y - 1, Z - 4, A - 5

  4. W - 4, X - 3, Y - 1, Z - 2, A - 5

  5. W - 3, X - 2, Y - 1, Z - 4, A - 5
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pseudomonas putida is used in bio-remediation, and is the world’s first patented organism. Thiobacillus thiooxidans can use sulfur and convert it into sulfuric acid, which can be used in Bio leaching. Bacillus thuringiensis is bacteria that produce a toxin called Bt toxin due to its plasmid, that kill insects. Thus it is used as bio-insecticides.  Ralstonia eutropha bacteria contain oxygen tolerant hydrogenases that are being used to investigate use in bio fuels. Anabaena is a filamentous cyanobacteria that can fix atmospheric nitrogen and thus is used as bio fertilizer.

Multiple choice

Methane oxidising bacteria help in petroleum prospecting by

  1. producing methane in presence of petrol deposits

  2. producing methane in absence of petrol deposits

  3. oxidising the aliphatic hydrocarbon

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

Methane-oxidising bacteria (methanotrophs) consume methane that reaches the soil surface. In areas without petroleum deposits, methane from deep geological sources reaches the surface and is consumed by methanotrophs, creating detectable methane anomalies. Where petroleum deposits exist, they act as barriers, reducing surface methane flux and methanotroph activity. This inverse relationship helps identify petroleum prospecting targets.

Multiple choice

Which of the following help(s) the helical bacteria, spirochetes to travel through viscous substances such as mucus or mud?

  1. Basal body

  2. External flagella

  3. L and P rings

  4. M ring

  5. Axial filament
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Spirochetes have two or more specialized flagella (endoflagella) arising from opposite poles of the cell, which together constitute the so called axial filament that is located within the periplasmic space between the flexible cell wall and an outer sheath. The rotation of the axial filament relative to the cell body causes the entire bacterium to move forward in a corkscrew-like motion even through material viscous enough to prevent the passage of normally flagellated bacteria. Each axial filament is composed of fibrils extending toward each other between two layers of the cell wall.

Multiple choice

Give an example for a bacterium, which moves with the help of flagella?

  1. Proteus

  2. Klebsiella

  3. Shigella

  4. Clostridium perfringens

  5. Aspergillus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Motile bacteria move about with structures called flagella. Many species in this family are highly motile with numerous flagella that allow several different modes of locomotion. Most of these movements are directly tied to the differential expression of flagella and other factors. When in liquid environments normal movement is facilitated by swimming.

Multiple choice

Which of the given prokaryotic structure is found in Bacillus but absent in Escherichia, helps to give negative charge to its cell wall?

  1. LPS

  2. PHB

  3. Endotoxins

  4. Teichoic acids

  5. Braun’s lipoprotein
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

They are polymers of glycerol or ribitol joined by phosphate groups and are not present in gram negative bacteria like Escherichia. They give the gram positive cell wall of Bacillus an overall negative charge due to the presence of phosphodiester bonds between teichoic acid monomers.

Multiple choice

Of the following which type of endospore location is observed in the organism Bacillus subtilis?

  1. Terminal spore

  2. Terminal spore with swollen sporangium

  3. Central spore

  4. Subterminal spore

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

Subterminal endospores are those between these two extremes usually seen far enough towards the poles but close enough to the center so as not to be considered either terminal or central. Examples of bacteria having subterminal endospore include Bacillus subtilis.

Multiple choice

The buffering capacity of saliva is against which kind of bacteria?

  1. Acidogenic

  2. Polymorphic

  3. Intercellular

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

Buffer capacity of saliva implies its acid-neutralizing power. Acidogenic organisms produce acids in the oral cavity, which leads to demineralization of tooth structure. These acids are neutralized with the help of buffers like bicarbonates and phosphates.

Multiple choice

Methyl-accepting chemotaxis proteins of bacteria ________.

  1. help to guide the bacterium since they are directly connected to the flagellar motor

  2. can only sense conditions that are favorable for bacterial growth

  3. tell the bacterium which way to go

  4. integrate multiple signals through a two component phospho-relay system
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Integrate multiple signals through a two component phospho-relay system. The methyl-accepting chemotaxis proteins are present on the outer surface of the bacteria. They are chemical sensors that help the bacteria to sense components present in its surroundings.

Multiple choice

Most of the Legionellas are pathogenic to amoeba. Which species of legionella was isolated from the biopurification systems of wood processing plants in 2015 that has no significant negative effect on growth or replication of the amoeba?

  1. Legionella pneumophila

  2. Legionella norrlandica

  3. Lactobacillus moravica

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

Legionella norrlandica isolated in 2015 from the biopurification systems of wood processing plants that has no significant negative effect on the growth or replication of the amoeba.