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 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

In 1995, Craig Venter, Hamilton Smith, Claire Fraser and colleagues at TIGR (The Institute for Genomic Research) elucidated the first complete genome sequence of a microorganism. Which was the organism whose complete genome sequence was elucidated?

  1. Zymomonas mobilis

  2. Burkholderia pseudomallei

  3. Haemophilus influenzae

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

Haemophilus influenzae was the first microorganism whose genome was sequenced. In 1995, Craig Venter, Hamilton Smith, Claire Fraser and colleagues at TIGR (The Institute for Genomic Research) elucidated the first complete genome sequence of Haemophilus influenzae.

Multiple choice

The diatoms are one of the largest and ecologically most significant groups of organisms on Earth. Which diatom is responsible for producing about a quarter of all the oxygen within Earth's biosphere?

  1. Bacteriastrum

  2. Ditylum brightwelli

  3. Odontella aurita

  4. Phaeodactylum tricornutum

  5. Navicula
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Navicula is a genus of boat-shaped diatom.Navicula play an important role in global ecology, producing about a quarter of all the oxygen within Earth's biosphere and serving as keystone species in the food chain of many environments where they provide a staple for the diets of many aquatic species.

Multiple choice

Choose the option that shows the correct pairing of the products with their corresponding microorganisms.

 
P. Citric acid i. Micromonospora purpurea
Q. Polyhydroxyalkonates ii. Zymomonas mobilis
R. Gentamycin iii. Aspergillus niger
S. Ethanol iv. Ralstonia eutropha

  1. P - i, Q - ii, R - iii, S - iv

  2. P - ii, Q - iii, R - i, S - iv

  3. P - iii, Q - iv, R - i, S - ii

  4. P - iii, Q - i, R - iv, S - ii

  5. P - iv, Q - ii, R - iii, S - i
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Citric acid is obtained from Aspergillus niger. Polyhydroxyalkonates are obtained from Ralstonia eutropha. Gentamycin is obtained from Micromonospora purpurea. Ethanol is obtained from Zymomonas mobilis.