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 bacteria is also called Klebs-Lِffler bacillus?

  1. Corynebacterium diphtheriae

  2. Enterococcus faecium

  3. Clostridium botulinum

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

Corynebacterium diphtheriae is a pathogenic bacterium that causes diphtheria. It is also known as the Klebs-Lِffler bacillus, because it was discovered in 1884 by German bacteriologists Edwin Klebs (1834 - 1912) and Friedrich Lِffler (1852 - 1915).

Multiple choice

Which of the following statements is true about log-phase growth of bacteria?

  1. During log-phase, nutrients are metabolised at minimum speed.

  2. Log-phase is the first phase of growth and is a period of slow growth.

  3. Log-phase is the third phase of growth and caused by depleted nutrients.

  4. During log-phase, calculations of growth rate and generation time of bacteria are done.

  5. Log-phase is the final phase of growth where the bacteria run out of nutrients and die.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This is the correct answer. Bacterial growth follows four phases. The log-phase is the second phase and marked by rapid exponential growth. The rate at which cells grow during log-phase is known as the growth rate (k) and the time it takes the cells to double is known as the generation time (g).

Multiple choice

The most common mode of nutrition in prokaryotic microbes is

  1. chemoheterotroph

  2. chemoautotroph

  3. photoheterotroph

  4. photoautotroph

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

Chemoheterotroph is the most common nutritional mode in prokaryotes. They use organic molecules as an energy source (for example, sugar) and use organic molecules as a carbon source (for example, proteins, sugars, fats, nucleic acids, etc.).

Multiple choice

“Quorum sensing” is a process of detecting surrounding cells, which are found in

  1. Halothiobacillus neapolitanus

  2. Planctomycetes

  3. Myxobacteria

  4. Bacteriophages

  5. Myxococcus xanthus
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When starved of amino acids, Myxobacteria detect surrounding cells in a process known as quorum sensing. They migrate towards each other and aggregate to form fruiting bodies up to 500 micrometres long and contain approximately 1,00,000 bacterial cells. About one in 10 cells migrate to the top of these fruiting bodies and differentiate into a specialised dormant state called myxospores, which are more resistant to drying and other adverse environmental conditions than ordinary cells.

Multiple choice

Which of the following statements are correct with reference to the action of bacteria?

A. Ammonifying bacteria release ammonia in the soil by decay and putrefaction. B. Nitrifying bacteria convert ammonia to nitrates directly. C. Nitrogen fixing bacteria can be symbiotic or non-symbiotic. D. Acetobacter aceti helps in the production of acetone. E. Mycoderma aceti converts sugar solution to acetic acid.

  1. A, C and E

  2. Only A and C

  3. B, C and D

  4. Only D and E

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

Ammonifying bacteria release ammonia in the soil by decay and putrefaction. Nitrogen fixing bacteria can be symbiotic or non-symbiotic. Mycoderma aceti converts sugar solution to acetic acid.