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

Rod shaped bacteria are called

  1. vibrio

  2. bacillus

  3. cocci

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bacillus is the correct term for rod-shaped bacteria. Vibrio are comma-shaped, cocci are spherical, so bacillus specifically describes the elongated, cylindrical shape.

Multiple choice

What is the relation between rhizobium and leguminous plants?

  1. Symbiotic

  2. Parasitic

  3. Heterotrophic

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

Rhizobium and leguminous plants share a mutual relation with each other, benefiting each other and getting benefited from each other and the relation is known as symbiotic relation.

Multiple choice

Which of the following pairs of bacteria shows positive Voges-Proskauer test?

  1. Enterobacter aerogenes and Escherichia coli

  2. Enterobacter aerogenes and Proteus mirabilis

  3. Escherichia coli and Klebsiella pneumoniae

  4. Escherichia coli and Proteus mirabilis

  5. Enterobacter aerogenes and Klebsiella pneumoniae
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Voges–Proskauer test is used to detect acetoin in bacterial broth culture. The test is performed by adding alpha-naphthol and potassium hydroxide to the Voges-Proskauer broth,  which has been inoculated with bacteria. A cherry red colour indicates a positive result, while a yellow-brown color indicates a negative result. Both Enterobacter aerogenes and Klebsiella pneumoniae give positive Voges–Proskauer test.

Multiple choice

Which of the following is the correct sequence of nodule formation after multiple interactions between Rhizobium and roots of the host plant?

(a) The infected root hair curls. (b) The nodule establishes a direct vascular connection with the host. (c) Bacteria gets modified into rod-shaped bacteroids. (d) Bacteria contacts a susceptible root hair and divide.

  1. c, a, d, b

  2. d, a, b, c

  3. b, a, c, d

  4. d, a, c, b

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The correct sequence is d, a, c, b.

Multiple choice

What are the mutants that cannot grow on minimal medium and requires nutrient supplements called?

  1. Auxotrophs

  2. Prototrophs

  3. Heterotrophs

  4. Lithotrophs

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

Auxotrophs would be the mutant cells that are not capable of utilizing certain nutrients or synthesizing certain compounds. Auxotroph is a mutant that requires nutritive(s) not needed by the wild type (prototroph). Auxotrophic mutations have been extensively used for the study of biochemical pathways and for the identification enzymes catalyzing particular metabolic steps. In the example of bacteria capable of utilizing lactose as a nutrient source, the ability to lactose is denoted by lac+ and the inability to utilize lactose is denoted lac-.

Multiple choice

Which of these is NOT a process of nitrogen cycle occurring in nature?

  1. Starch is produced by photosynthesis

  2. Blue-green algae and bacteria fix nitrogen

  3. Uptake of nitrate by plants

  4. Lightning fixes nitrogen

  5. Death of organisms and nitrogenous waste excretion brings nitrogenous materials back to soil.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photosynthesis is not a part of nitrogen cycle.