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 correctly describes enrichment medium?

  1. It is a selective medium.

  2. It is a differential medium.

  3. It favours the growth of very small number of desired microbes to detectable limits.

  4. It is a reducing medium and favours the growth of anaerobes.

  5. It is a complex medium.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Enrichment culture medium is used to increase the number of desired type of organisms to detectable limits.

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

Capnophiles are the microbes that are grown

  1. at high CO2 concentration

  2. at low CO2 concentration

  3. using CO2 incubators

  4. using CO2-generating packet incubators

  5. Both (3) and (4)
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct answer.

Multiple choice

The term Hyperthermophiles stands for?

  1. Hperthermophiles are also known as extreme thermophiles.

  2. Microbes that can grow at 80 degrees or higher

  3. Organisms living in hot springs associated with volcanic activity

  4. Both the options 1, 2 and 3 are correct

  5. Organisms that grow in sunlit soil
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

True because all the above three options are for hyperthermophiles only

Multiple choice

Which of the following organisms are carotenoid producers?

  1. Choanephora cucurbitarum,Phycomyces blakesleeanus, and Streptomyces chrestomyceticus

  2. Pedicoccus cerevisiae, Chromohalobacter beijerinckii and Bacillus species

  3. Candida krusei, Penicillium camemberti and Leuconostoc plantarum

  4. Pseudomonas denitrificans, Bacillus megaterium and Streptomyces olivaceus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

All these organisms produce carotenoids. Phycomyces blakesleeanus and Choanephora cucurbitarum produce beta carotene and Streptomyces chrestomyceticus produces lycopene.

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.

Multiple choice

Which of the following microorganisms yields the greatest amount of vitamin B12?

  1. Rhodopseudomonas protamicus

  2. Rhodopseudomonas spheroides

  3. Pseudomonas denitrificans

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

Rhodopseudomonas protamicus is a hybrid strain of Rhodopseudomonas spheroides and Protaminobacter rubber and can produce as high as 135 mg/l of vitamin B12 utilising carbon source. Thus, it is the strain that yields the greatest amount of vitamin B12.

Multiple choice

Match the given polymers with the organisms which produce them:

Polymer Organism
1. Pollulan A. Sclerotium glucanicum
2. Gellan B. Alcaligenes faecalis
3. Curdlan C. Pseudomonas elodea
4. Scleroglucan D. Aureobasidium sps
  1. 1. Pollulan C. Pseudomonas elodea
    2. Gellan D. Aureobasidium sps
    3. Curdlan A. Sclerotium glucanicum
    4. Scleroglucan B. Alcaligenes faecalis
  2. 1. Pollulan
    D. Aureobasidium sps
    2. Gellan C. Pseudomonas elodea
    3. Curdlan B. Alcaligenes faecalis
    4. Scleroglucan A. Sclerotium glucanicum
  3. 1. Pollulan C. Pseudomonas elodea
    2. Gellan A. Sclerotium glucanicum
    3. Curdlan D. Aureobasidium sps
    4. Scleroglucan B. Alcaligenes faecalis
  4. 1. Pollulan A. Sclerotium glucanicum
    2. Gellan B. Alcaligenes faecalis
    3. Curdlan D. Aureobasidium sps
    4. Scleroglucan C. Pseudomonas elodea
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct match. Pollulan is produced by using the fungus Aureobasidium pollulans. Gellan is produced by Pseudomonas elodea. The exopolysaccharide curdlan is commercially produced by employing Alcaligenes faecalis. Scleroglucan is a fungal heoxpolysaccharide. It is commercially produced by Sclerotium glucanicum.

Multiple choice

The roots of _________ plants help in nitrogen fixation.

  1. green

  2. flowery

  3. pulse

  4. non-green
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pulse plants (legumes like beans, lentils, peas) have root nodules containing nitrogen-fixing bacteria that convert atmospheric nitrogen into usable forms. Green, flowery, and non-green plants don't necessarily have this association - only legumes among pulses have this specialized nitrogen-fixing ability.

Multiple choice

Nitrites and nitrates are converted into __________ by plants.

  1. nucleic acids

  2. amino acids

  3. sugars

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

Nitrites and nitrates are inorganic forms of nitrogen that plants absorb from soil and convert into organic compounds. Through nitrogen assimilation, these are reduced to ammonium and then incorporated into amino acids, which are the building blocks of proteins. This process is essential for plant growth and protein synthesis.