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

Which of the following is an example of chemosynthetic bacteria?

  1. Purple bacteria

  2. Escherichia coli

  3. Cyanobacteria

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

Nitrobacter is genus of mostly rod-shaped, gram-negative, and chemoautotrophic bacteria. Nitrobacter plays an important role,  in nitrogen cycle by oxidizing nitrite,  into nitrate in soil.

Multiple choice

Leaves of Azolla, a pteridophyte, house the colony of

  1. anabaena

  2. VAM

  3. rhizobium

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

Azolla is a small aquatic fern that has a symbiotic relationship with the cyanobacterium Anabaena azollae, which lives in its leaf cavities and fixes atmospheric nitrogen.

Multiple choice

Archaea were initially viewed as extremophiles living in harsh environments but they have also been found in habitats like soil, oceans etc. Which of the following is their ecological role?

  1. Nutrient absorption

  2. Sugar metabolism

  3. Ammonification

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

Archaea are very important for ammonification in rhizospheres. It is a process that includes transforming organically bound nitrogen from microbial or plant biomass to ammonia.

Multiple choice

In a mutualistic relationship, bacteria live in the roots of plants by forming nodules and provide fixed nitrogen to the plant. Which of the following kinds of nodules are found in alfalfa and clover?

  1. Legume nodules

  2. Perennial legume nodules

  3. Angular legume nodules

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

Perennial legume nodules are long finger-like nodules, half an inch in diameter. They can be found on alfalfa and clover. These nodules grow mostly around the tap root and live for quite a long time.

Multiple choice

Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia. Which of the following organisms is supposed to perform almost half of the nitrogen fixation in marine systems on a global scale?

  1. Gloeobacter

  2. Johannesbaptistia

  3. Nostoc

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

Trichodesmium belongs to the genus of filamentous cyanobacteria. It performs almost half of the nitrogen fixation in marine systems on a global scale.

Multiple choice

Which of the following are archaebacteria?

  1. Pseudomonads

  2. Chlamydias

  3. Green sulfur bacteria

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

Methanogenesis or biomethanation is the formation of methane by microbes known as methanogens. Organisms capable of producing methane have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria.

Multiple choice

Root nodules are helpful in ____ fixation.

  1. C

  2. H

  3. N

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

Root nodules in leguminous plants contain symbiotic bacteria (like Rhizobium) that fix atmospheric nitrogen into a form usable by plants.