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 gram-positive bacteria having ability to oxidize glucose by Entner–Doudoroff pathway?

  1. Bacillus subtilis

  2. Enterococcus faecalis

  3. Escherichia coli

  4. Xanthomonas campestris

  5. Zymomonas mobilis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Very few gram-positive bacteria have ability to oxidize glucose by Entner–Doudoroff pathway. Enterococcus faecalis is an example of gram-positive bacteria having ability to oxidize glucose by Entner–Doudoroff pathway.

Multiple choice

Which of the following is a pair of dissimilative sulfur reducers?

  1. Archaeoglobus and Desulfobulbus

  2. Campylobacter and Desulfuromonas

  3. Desulfococcus and Desulfobacter

  4. Archaeoglobus and Desulfuromonas

  5. Campylobacter and Desulfobacter
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In dissimilative sulfur reduction, elemental sulfur is reduced to hydrogen sulfide. Dissimilative sulfur reducers reduce elemental sulfur to hydrogen sulfide. Campylobacter and Desulfuromonas are dissimilative sulfur reducers.

Multiple choice

Which of the following are examples of barophilic bacteria?

  1. Photobacterium profundum
  2. Schewenella benthica
  3. Staphylococcus aureus
  4. Colwellia psychrerythraea
  5. Micrococcus luteus Select the correct answer.

  1. 1, 2 and 3 only

  2. 1, 2 and 4 only

  3. 2, 3 and 4 only

  4. 3, 4 and 5 only

  5. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Barophiles (piezophiles or barophilic bacteria) are bacteria which grow preferentially or exclusively at moderately high hydrostatic pressures. Examples: Photobacterium profundum, Schewenella benthica, Colwellia psychrerythraea

Multiple choice

Which of the following is a pair of hyperthermophilic bacteria?

  1. Anaerobaculum and Sulfobacillus

  2. Anaerobaculum and Pyrodictium

  3. Methanopyrus and Sulfobacillus

  4. Methanopyrus and Pyrodictium

  5. Pyrodictium and Sulfobacillus
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Methanopyrus is a rod-shaped hyperthermophilic methanogen, discovered on the wall of a black smoker from the Gulf of California at a depth of 2000 m, at temperatures of 84–110 °C. Pyrodictium is a genus of submarine hyperthermophilic archaea whose optimal growth temperature ranges is 80 to 105 °C.

Multiple choice

Which of the following is a set of acidophiles only?

  1. Escherichia, Euglena, Sulfolobus, Picrophilus

  2. Alicyclobacillus, Escherichia, Natronobacterium, Paramecium

  3. Alicyclobacillus, Ferroplasma, Picrophilus, Sulfolobus

  4. Escherichia, Ferroplasma, Natronobacterium, Picrophilus

  5. Escherichia, Euglena, Natronobacterium, Paramecium
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Alicyclobacillus, Ferroplasma, Picrophilus, and Sulfolobus: All are acidophiles (optimum growth between pH 0 and 5.5).

Multiple choice

Which of the following statements is true about Aerotolerant anaerobes?

  1. They are completely dependent on atmospheric oxygen for growth.

  2. They are able to grow under anaerobic conditions but develop most rapidly in an aerobic environment.

  3. They grow equally well in presence or absence of oxygen.

  4. They do not tolerate oxygen and dies in its presence.

  5. They thrive in an environment low in oxygen.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aerotolerant anaerobe grow equally well in presence or absence of oxygen.

Multiple choice

Which of the following is a genus of microaerophilic bacteria?

  1. Campylobacter

  2. Bacteroides

  3. Clostridium

  4. Bacillus

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

Campylobacter is a genus of bacteria that are Gram-negative, spiral, and microaerophilic. Microaerophiles require oxygen levels in the range of 2 to 10% for their growth and are damaged by the normal atmospheric level of oxygen (20%).

Multiple choice

Which of the following is a sulphate reducing bacterium?

  1. Gallionella ferruginea

  2. Desulfotomaculum carboxydivorans

  3. Rhodospirillum rubrum

  4. Beijerinckia derxii

  5. Streptococcus thermophilus
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Desulfotomaculum carboxydivorans is a moderately thermophilic, anaerobic, chemolithoheterotrophic, sulfate-reducing bacterium.

Multiple choice

Which of the following statement/statements is/are true of microbial biofilm?

  1. Biofilms are composed of group of microorganisms adhering to environmental surfaces.
  2. Biofilms can form only on non-living surfaces.
  3. Natural biofilms always consist of only a single microbial species. Select the correct answer.

  1. Only 1

  2. Only 2

  3. 3 only

  4. 1 and 2

  5. 2 and 3

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

A biofilm is any group of microorganisms in which cells stick to each other adhering on a surface.

Multiple choice

Which of the following is a set of obligate anaerobes only?

  1. Nocardia, Peptostreptococcus, Propionibacterium, Treponema

  2. Nocardia, Peptostreptococcus, Treponema, Veillonella

  3. Peptostreptococcus, Propionibacterium, Treponema, Veillonella

  4. Peptostreptococcus, Propionibacterium, Staphylococcus, Treponema

  5. Propionibacterium, Staphylococcus, Treponema, Veillonella
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Peptostreptococcus, Propionibacterium, Treponema, Veillonella: All are obligate anaerobes.

Multiple choice

Which of the following groups of bacteria are called gliding bacteria?

  1. Mycobacteria and Myxobacteria

  2. Mycobacteria and Cytophagales

  3. Myxobacteria and Cytophagales

  4. Cytophagales and Rickettsiae

  5. Rickettsiae and Chlamydiae
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Myxobacteria and Cytophagales are called gliding bacteria on the basis of their gliding mobility on solid surfaces.

Multiple choice

Which of the following microorganisms have least G + C moles %?

  1. Bacillus subtilis

  2. Escherichia coli

  3. Mycobacterium tuberculosis

  4. Spirillum linum

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

In molecular biology and genetics, guanine-cytosine content (GC-content) is the percentage of nitrogenous bases on a DNA molecule that are either guanine or cytosine. DNA with high GC-content is more stable than DNA with low GC-content. Among given microbes Spirillum linum have least G+C moles % (28-30).