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

Identify the correct pair of characters of a bacterium which is used in the production of methane.
(i)   Recyclers of inorganic nutrients
(ii)  Present in stomach of cattle
(iii) Obtain energy from sunlight
(iv) Aerobes

  1. ii, iii

  2. i, ii

  3. i, iv

  4. iii, iv
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Methanogens are anaerobic bacteria (not aerobes) that recycle inorganic nutrients and are found in the rumen of cattle to aid in cellulose digestion.

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

The order of bacteria active in conversion of organic wastes into biogas is

  1. Hydrolytic $\rightarrow$ Acetogenic $\rightarrow$ Methanogenic
  2. Methanogenic $\rightarrow$ Acetogenic $\rightarrow$ Hydrolytic
  3. Methanogenic $\rightarrow$ Hydrolytic $\rightarrow$ Acetogenic
  4. Acetogenic $\rightarrow$ Methanogenic $\rightarrow$ Hydrolytic
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The order of bacteria active in the conversion of organic wastes into biogas is hydrolytic, acetogenic, methanogenic. 

Hydrolytic- Insoluble organic polymers, such as carbohydrates, are broken down to soluble derivatives which are used by bacteria.

Acetogenic- Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. These bacteria convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide.

Methanogenic- The methanogens convert the product of acetogenic step to methane and carbon dioxide. The produced gas consisting of methane, carbon dioxide, and traces of other ‘contaminant’ gases is known as biogas.

So, the correct answer is 'Hydrolytic $\rightarrow$ Acetogenic $\rightarrow$ Methanogenic'.

Multiple choice biology food production food production and microorganisms microbial products - food, medicines and industrial products uses of microorganisms

A number of organic compounds can be decomposed by

  1. Pseudomonas

  2. Mycoplasma

  3. Chemolithotrophs

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

Organic compounds like plant and animal residues are present in the soil. These organic compounds are broken down by a large number of bacteria, fungi, larger organisms. Bacteria like Pseudomonas lives in the soil and decomposes organic compounds and releases carbon dioxide, energy, water and other plant nutrients.

Thus, the correct answer is 'Pseudomonas.'

Multiple choice biology food production food production and microorganisms microbial products - food, medicines and industrial products uses of microorganisms

The most thoroughly studied of the known bacteria-plant interactions is the :-

  1. Gall formation on certain angiosperms by Agrobacterium

  2. Nodulation of Sesbania stems by nitrogen fixing bacteria

  3. Plant growth stimulation by phosphate solubilising bacteria

  4. Cyanobacterial symbiosis with some aquatic ferns
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Agrobacterium tumefaciens is called a natural plant genetic engineer. Using Agrobacterium vector, nematode specific genes were introduced into the host plant. The introduction was as such that it produced both sense and anti-sense RNA in the host cells. These two RNA's being complementary to each other formed a double-stranded (ds-RNA) that initiated RNAi and thus, silenced the specific mRNA of the nematode. The Agrobacterium is most widely studied of the known bacteria-plant interactions.
So the correct answer is 'Option A'.
Multiple choice biology food production food production and microorganisms microbial products - food, medicines and industrial products uses of microorganisms

Which is not a bacterial action?

  1. Nitrogen fixation

  2. Emulsification of fat

  3. Sewage disposal

  4. Ripening of cream
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • Nitrogen fixation is a process by which atmospheric nitrogen is converted into ammonium compounds and made available for plants. Examples include Rhizobium, Azotobacter.
  • Many bacteria are also involved in the sewage disposal process. Mostly saprophytic aerobic bacteria are used in treatment plants.
  • During the process of ripening of cream, Lactic acid bacteria are used. These bacteria convert lactose into acid and results in the curdling of cream.
Thus, the correct answer is 'Emulsification of fat.'