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 zoology microbes in human welfare biofertilizers microbes as biocontrol agents and biofertilizers manuring

In Nostoc, the enzyme nitrogenase occurs in

  1. Vegetative cells

  2. Heterocysts

  3. Only in hormogones

  4. Both A and B
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Nostoc is a cyanobacteria. It has ability to fix atmospheric nitrogen. It converts nitrogen into ammonia. The heterocysts present in it are specialized cyanobacterial cells for nitrogen fixation. It contains enzyme nitrogenase. Nitrogenase is inactivated by oxygen. Hence, the heterocyst creates a micro anaerobic environment.
Thus, the correct answer is 'Heterocysts.'
Multiple choice zoology microbes in human welfare biofertilizers microbes as biocontrol agents and biofertilizers manuring

I. Unicellular, colonial, filamentous, marine or terrestrial forms.
II. The colonies are surrounded by a gelatinous sheath.
III. Some can fix atmospheric nitrogen in specialized cells called heterocysts.
IV. They often form blooms in water bodies.
These above characters are seen in

  1. Archaebacteria

  2. Cyanobacteria

  3. Chrysophytes

  4. Dinoflagellates

  5. Slime Moulds
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cyanobacteria are also called as Blue green algae. They are unicellular, colonial, filamentous prokaryotes. They are found in marine and terrestrial habitats. The colonies are surrounded by a gelatinous sheath. They are photosynthetic bacteria. They often form blooms in water bodies and results in eutrophication. Some Cyanobacteria like Nostoc can fix atmospheric nitrogen in specialized cells called heterocysts and make it available to plants.

Thus, the correct answer is 'Cyanobacteria.'

Multiple choice zoology microbes in human welfare biofertilizers microbes as biocontrol agents and biofertilizers manuring

Azolla possesses symbiotic association with

  1. <p>Anabaena</p>

  2. <p>Nostoc</p>

  3. <p>Azospirillum</p>

  4. <p>Rhizobium</p>
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Azolla is a small aquatic fern that maintains a symbiotic relationship with the cyanobacterium Anabaena azollae. This bacterium lives in the leaf cavities of the fern and fixes nitrogen for the plant.

Multiple choice zoology microbes in human welfare biofertilizers microbes as biocontrol agents and biofertilizers manuring

Cynobacteria are:

  1. mosses which attack bacteria.

  2. bacteria which attack cynophyceace

  3. autotrophic organism with phycocyanin

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The cyanobacteria (also referred to as blue-green algae) have chlorophyll a similar to green plants and are photosynthetic autotrophs. The cyanobacteria are unicellular, colonial or filamentous, fresh-water marine or terrestrial algae. The colonies are generally surrounded by a gelatinous sheath. They often form blooms in polluted water bodies. Some of these organisms can fix atmospheric nitrogen in specialized cells called heterocysts, e.g, Nostoc and Anabaena.

So the correct option is "autotrophic organisms with phycocyanin".

Multiple choice zoology microbes in human welfare biofertilizers microbes as biocontrol agents and biofertilizers manuring

Which of the following plants can act as a biofertilizer

  1. Nostoc

  2. Funaria

  3. Volvox

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

Nostoc belongs to cyanobacteria genus, and it can be used as biofertilizer. It is also called the blue-green algae. Nostoc converts atmospheric nitrogen into ammonia, which can be further converted to a suitable form for plant growth. Biofertilizers enhance the quality of plants and soil.

So the correct answer is 'Nostoc'.

Multiple choice zoology microbes in human welfare biofertilizers microbes as biocontrol agents and biofertilizers manuring

Which of the following is the pair of biofertilizers?

  1. Azolla and BGA

  2. Nostoc and legume

  3. Rhizobium and grasses

  4. Salmonella and E. coli
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Biofertilizers are the suspension of microorganism which mainly increases the growth of the plants. These secrete the growth promoting substances. The microorganisms in bio-fertilizers restore the soil's natural nutrient cycle and build soil organic matter. Bio-fertilizers such as Rhizobium, Azotobacter, Azospirilium and blue-green algae (BGA) are used. Anabaena in association with water fern Azolla contributes nitrogen up to 60 kg/ha/season and also enriches soils with organic matter.

So, the correct answer is option A.

Multiple choice botany taxonomy and systematic botany taxonomy and systematics systematics of living world kingdom plantae plant taxonomy classification of biodiversity

A mutant strain of Neurospora which fails to grow on a minimal medium unless supplemented with a nutrient is called

  1. Auxotroph

  2. Autotroph

  3. Heterotroph

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

An auxotroph is a mutant organism that requires a specific nutrient for growth that the wild-type strain can synthesize on its own.

Multiple choice evs louis pasteur contribution of louis pasteur discoveries by louis pasteur discovery of microorganisms

Micro-organisms having optimum temperature for growth below $15^0$ C which cannot grow above $20^0$ C are called

  1. Mesophiles

  2. Thermophiles

  3. Psychrophiles

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(A)Mesophile is an organism that grows in a moderate temperature from 20-45 degree Celcius.

(B)A thermophile is an organism that grows in a relatively high temperature from 41-122 degree Celcius.
(C) is an organism that grows in a relatively low temperature from below 15-degree Celcius.
So, the correct option is 'Psychrophiles'.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Chemosynthesizers can convert chemicals into biomass, and many types of chemosynthetic organisms congregate near hydrothermal vents, where chemicals are abundant.
Predict why there would be higher biomass and greater primary production of organisms living in the hydrothermal vent areas, in contrast to the areas outside the vent areas.

  1. The vents release an abundance of chemicals the organisms living there can use in the production of energy molecules.

  2. The heat released from the vents oxidizes chemicals in the water that organisms consume.

  3. It is too cold outside the vent areas, so most of the organisms live within the vent areas.

  4. Predators are rare in the vent areas, so organisms rarely venture out beyond the immediate vent area.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hydrothermal vents are abundant in chemical substances that are released by the core of the earth. These vents are devoid of light and have a temperature of about 350$^o$C. Therefore, this habitat can help only those organisms to survive which do not use light as a source of energy, that is autotrophs of this food chain should be able to synthesize food from chemicals present in the surrounding- example archea while withstanding the extreme temperature

So, the correct answer is 'The vents release an abundance of chemicals the organisms living there can use in the production of energy molecules'

Multiple choice botany adaptations to different ecosystems lichen lichens lichens ( the nature's pioneers )

Which of the following share same mode of nutrition?

  1. Rhizobium and lichens

  2. Lichens and Mycorrhizae

  3. Mycorrhizae and Rhizobium

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Rhizobium is a genus of bacteria associated with the formation of root nodules on plants. These bacteria live in symbiosis with legumes. They take in nitrogen from the atmosphere and pass it on to the plant, allowing it to grow in soil low in nitrogen.
  • A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi in a symbiotic relationship. 
  • Mycorrhizal fungi colonize the plant's root system and develop a symbiotic association called “mycorrhiza” They form a network of fine filaments that associate with plant roots and draw nutrients and water from the soil that the root system would not be able to access otherwise.
  • Lichens, Rhizobium and Mycorrhizae  have symbiotic relationships and follow same mode of nutrition.
  • So the correct answer is " All the above".
Multiple choice biology biotechnology and genetic engineering stds and infertility gm crops biotechnology

In the formation of ascorbic acid, the micro-organism used is

  1. Acetobacter

  2. Streptomyces sp.

  3. Bacillus megatherium

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

Acetobacter suboxydans is a gram-negative bacteria of the order rhodospirilla. It is used in the formation of ascorbic acid. A. suboxydans is widely used commercially in the production of ketonic acids like ascorbic acid (Vitamin C). 

Multiple choice biology biotechnology and genetic engineering stds and infertility gm crops biotechnology

Which one of the following pairs is not correctly matched?

  1. Spirulina - Single cell protein

  2. Rhizobium - Biofertilizer

  3. Streptomyces - Antibiotic

  4. Serratia - Drug addiction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Serratia is a genus of gram negative, facultatively anaerobic, rod-shaped bacteria of the enterobacteriaceae family. The most common species S. marcescens, is normally the only pathogen and usually causes nosocomial infections.