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 introduction to microbiology microbial pollution control environmental use of microorganism microbes in waste treatment and biogas

Which one is the most important role of microorganisms for the well being of humans?

  1. Sewage treatment

  2. Production of methane

  3. Conversion of milk to curd

  4. Biological control of plants disease
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Answer is option C i.e. "Conversion of milk to curd"

Microorganisms help in the production of many food items, making medicines, keeping the environment clean, in manufacturing and in research. 
Conversion of milk to curd is the considered as an important role in the micro organism for the well being of humans. . Bacteria like Lactobacillus can be used to make curd from milk by process of fermentation.

Multiple choice zoology introduction to microbiology microbial pollution control environmental use of microorganism microbes in waste treatment and biogas

Select the correct statement from the following.

  1. Methanobacterium is an aerobic bacterium found in rumen of cattle.

  2. Biogas commonly called gobar gas is pure methane.

  3. Activated sludge sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria.

  4. Biogas is produced by the activity of aerobic bacteria on animal waste.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Methanobacterium is an anaerobic bacterium..
Biogas is a mixture of gases (predominantly methane).
Biogas is produced by the activity of anaerobic bacteria.
Correct answer-C
Multiple choice zoology bio-geo chemical cycles in nature nutrient cycles- flow of substances carbon cycle biogeochemical cycles - gaseous

Which bacteria is responsible to fix nitrogen in leguminous plants?

  1. Azotobacter

  2. Rhizobium

  3. Clostridium

  4. Saccharomycese
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Some bacteria maintain the soil fertility and others enhance it. The fertility of the soil is proportional to the nitrogen content. Nitrogen is an important ingredient in the structure and function of the living beings. Nitrogen-fixing bacteria like Azotobacter, Clostridium live free in the soil and fix atmospheric nitrogen. Rhizobium like bacteria live symbiotically with root systems of leguminous plants and fix from the atmospheric nitrogen. Therefore, the correct answer is option B.

Multiple choice zoology bio-geo chemical cycles in nature nutrient cycles- flow of substances carbon cycle biogeochemical cycles - gaseous

The microbial biofertilizers which can act both symbiotically and non-symbiotically to increases soil fertility are

  1. Azotobacter

  2. Rhizobium

  3. Clostridium

  4. `Nostoc and Anabaena
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Azotobacter can act both as symbiotically and non symbiotically to increase soil fertility. It Infuse the soil with antibiotic pesticides and inhabit the spread of soil borne diseases like pythium and phytophthora.

Multiple choice zoology bio-geo chemical cycles in nature nutrient cycles- flow of substances carbon cycle biogeochemical cycles - gaseous

The bacterium nitrobacter converts

  1. Nitrogen to nitrite

  2. Ammonia to nitrite

  3. Nitrite to nitrate

  4. Nitrate to nitrite
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Nitrification is a two step process of converting ammonia into nitrites and nitrites into nitrates. Bacteria converting ammonia into nitrites includes Nitrosomonas. Bacteria converting nitrites to nitrates includes Nitrobacter.

Thus, the correct answer is 'Nitrite to nitrate.'

Multiple choice zoology bio-geo chemical cycles in nature nutrient cycles- flow of substances carbon cycle biogeochemical cycles - gaseous

Nitrogen fixing bacteria- anabaena - are found in the plant ______

  1. Azolla leaves

  2. Cycas corolloid roots

  3. Anthoceros body

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Anabaena are the one type of cyanobacteria, present in the leaves of Azolla, Corolloid roots of Cycas, Anthoceros body. They perform symbiotic Nitrogen fixation.
So the correct option is 'All of these'.
Multiple choice zoology bio-geo chemical cycles in nature nutrient cycles- flow of substances carbon cycle biogeochemical cycles - gaseous

Which one of the following is a wrong statement ? 

  1. Phosphorus is a constituent of cell membranes, certain nucleic acids and all proteins

  2. Nitrosomonas and Nitrobacter are chemoautotrophs

  3. Anabaena and Nostoc are capable of fixing nitrogen in free living state

  4. Root nodule forming nitrogen fixers live as aerobes under free living conditions
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
A. Phosphorus is constituent of cell membranes in the form of phospholipids and also present in nucleic acids as phosphate in the sugar-phosphate backbone.
B. Nitrosomonas and Nitrobacter are nitrifying bacteria. These bacteria derive energy by oxidizing inorganic nitrogenous compounds. Hence, they are called chemoautotrophs.
C. Anabaena and Nostoc are cyanobacteria (also known as blue-green algae). They are free-living bacteria and can fix nitrogen because they have specialized cells called heterocysts with the help of which they can fix atmospheric nitrogen.
D. Root nodule forming nitrogen-fixing microbes live freely in the soil as aerobes. They form a symbiotic association with the roots of plants when some chemicals or factors are released by the plants. For example, Rhizobium.
Hence, statement A is incorrect.
So, the correct answer is 'Phosphorus is a constituent of cell membranes, certain nucleic acids, and all proteins'.
Multiple choice zoology bio-geo chemical cycles in nature nutrient cycles- flow of substances carbon cycle biogeochemical cycles - gaseous

The bacteria ______ supply natural manure to paddy fields.

  1. Azolla

  2. Anabaena

  3. Azotobacter

  4. Nostoc
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The bacteria Azolla supplies natural manure to the paddy fields. Azolla is a gliding pteridophyte, which contains as endosymbiont the nitrogen-settling cyanobacterium Anabaena azollae (Nostocaceae family). 
Generally developed in the Asian districts, Azolla is either consolidated into the dirt before rice transplanting or developed as a double product alongside rice. 
So, the correct answer is A.
Multiple choice biology excretion - the wastage disposing system excretion in other organisms other excretory organ role of other organs in excretion

Organisms that excrete amino acid is

  1. Aminotelic

  2. Ammonotelic

  3. Ureotelic

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

Certain invertebrates like some molluscs (Unio, Limnaea, etc.) and some echinoderms (e.g., Asterias) excrete excess amino acids as such. These animals are called aminotelic and their mode of excretion is called aminotelism.

So, the correct option is 'Aminotelic'.

Multiple choice biology interdependence of organism and the environment food material and source sources of food and food habits of animals forests: our lifeline

Decomposers are

  1. Autotrophs

  2. Heterotrophs

  3. Autoheterotrophs

  4. Organotrophs
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Decomposers are heterotrophs feeding on the dead and decaying matter. More specifically decomposers are saprotrophs, which decompose the organic remains by secreting extracellular digestive enzymes. Due to degradation of organic remains, decomposers are also called as reducers. They are also known as mineralizers, as they release mineral trapped in organic remains.

Multiple choice botany biotechnology: general introduction microbiology: organisms in industry biotechnology commercial applications of biotechnology

Most widely used bacterium in plant genetic engineering, in relation to nitrogen fixation, is Klebsiella pneumoniae which can fix nitrogen under ................. conditions.

  1. Aerobic

  2. Anaerobic

  3. Laboratory

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium. It naturally occurs in the soil, and about 30% of strains can fix nitrogen in anaerobic conditions.

Multiple choice zoology bioenergy biogas environmental use of microorganism microbes in waste treatment and biogas

Bacteria involved in formation of gobar gas are

  1. Obligate aerobes

  2. Facultative anaerobes

  3. Obligate anaerobes

  4. Both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Biogas is produced from the fermentation of organic matter by the action of microbes. Such microbes are anaerobic i.e. they carry out fermentation in the absence of oxygen. Microbes which produce biogas are methanogenic bacteria which can be obligate anaerobes or they can be facultative anaerobes. Obligate anaerobes function only in absence of oxygen i.e. anaerobic conditions. Facultative anaerobes are the bacteria which normally function in aerobic conditions but they can switch to anaerobic respiration if oxygen is absent. Hence, both options B and C are correct.
So, the correct answer is 'Both B and C'.