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

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

The nitrogen gets converted into its oxides during

  1. lightening

  2. transpiration

  3. decomposition

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

Lightning provides the enormous energy needed to break the strong triple bond in atmospheric nitrogen (N2). This allows nitrogen to react with oxygen, forming nitrogen oxides like NO and NO2.

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.

Multiple choice

Which among the following statements does not characterise Escherichia coli (E. coli)?

  1. E. coli and other facultative anaerobes constitute about 0.1% of gut flora.

  2. E. coli is a gram-negative, facultatively aerobic, rod-shaped bacterium.

  3. E. coli is a very versatile host for the production of heterologous proteins.

  4. E. coli was one of the first organisms to have its genome sequenced.

  5. E. coli normally colonises an infant's gastrointestinal tract within 40 hours of birth.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Escherichia coli is a Gram-negative, facultatively anaerobic, rod-shaped bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms).

Multiple choice

The presence of which of the following elements is required for the formation of leghemoglobin in N2 fixing bacteria?

  1. Cobalt

  2. Copper

  3. Molybdenum

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

Cobalt is required for the synthesis of leghemoglobin and for the growth of legumes relying on symbiotically fixed nitrogen. It is an essential micronutrient. It has been established that rhizobium and other N2 fixing microorganisms have an absolute cobalt requirement whether or not they are growing within nodules and regardless of whether they are dependent on a nitrogen supply from N2 fixation or from mineral nitrogen.

Multiple choice

A fecal sample suspected to contain pathogens was plated on nutrient agar in aerobic, anaerobic and microaerophilic environment. Growth was seen only on the plate kept under microaerophilic environment. Which of the following can be the suspected organism and the medium used to confirm it?

  1. Enterobacter and McConkey agar

  2. Campylobacter and Butzler's virion

  3. Bacteriodes and brain heart infusion agar

  4. Pseudomonas and cetrimide agar
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The suspected organism is campylobacter as it is a strict microaerophile. Confirmatory test can be done by plating on Butlezr's virion, which is selective for campylobacter.

Multiple choice

Septum formation in transverse binary fission occurs at the middle of the cell. However, there are some exceptions to it which often form septum near the pole. Which of the following bacteria is an exception to the general septum formation?

  1. Wild type E. coli

  2. Mutant E. coli

  3. Recombinant of E. coli and Bacillus subtilis

  4. Starved E. coli
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Some mutant E. coli often form the septum near the pole. This results in a very small daughter cell lacking DNA.