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 nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

How many organisms In the list given below are $N _2$ fixer autotrophs?
Azotobacter, Chromobum, Azospirillum, Rhodospirillum, Rhizobium, Nitrobacter, Aulosira, Nostoc, Osallatona

  1. Three

  2. Four

  3. Five

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

Nitrogen-fixing bacteria are capable of fixing atmospheric nitrogen to inorganic substances usable by plants. Example from the given list are Azetobactor, Azospirillum, Rhizobium, Nitrobactor and Nostoc.

So the correct answer is 'five'.

Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

Which of the following is a free living aerobic non - photosynthetic nitrogen-fixer ?

  1. $Rhizobium$
  2. $Azotobacter$
  3. $Azospirillum$
  4. $Nostoc$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Azotobacter is a free-living nitrogen-fixing bacterium, which is used as a biofertilizer in the cultivation of most crops. Azotobacter respires aerobically, receiving energy from redox reactions, using organic compounds as electron donors. Azotobacter can use a variety of carbohydrates, alcohols, and salts of organic acids as sources of carbon. 

Rhizobium fixes nitrogen by symbiotic association. Nostoc is photosynthetic. Azospirillum is anaerobic. 
So, the correct option is 'Azotobacter'.

Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

All of the following statements concerning the actinomycetous filamentous soil bacterium Frankia are correct except that Frankia

  1. Can induce root nodules on many plant species

  2. Can fix nitrogen in the free-living state

  3. Like Rhizobium, it usually infects its host plant through root hair deformation and stimulates cell proliferation in the host's cortex

  4. Forms specialized vesicles in which the nitrogenase is protected from oxygen by a chemical barrier involving triterpene hopanoids
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Frankia is a bacterium which grows in a symbiotic association with the roots of non-leguminous plants.  It can fix atmospheric nitrogen. It cannot fix nitrogen in free-living state.

So, the correct option is 'Can fix nitrogen in free-living state'.

Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

Bacteria involved in two-step conversion ammonia into nitrate are

  1. Azotobacter and Nitrosomonas

  2. Pseudomonas and Nitrobacter

  3. Azotobacter and Achromobacter

  4. Nitrosomonas and Nitrobacter
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nitrification is a process of conversion of ammonium ions to nitrites and nitrites to nitrates. It is a two-step process. The bacteria that carry out this process are called as nitrifying bacteria. Nitrosomonas, Nitrosospira, Nitrosococcus convert ammonia into nitrites. Nitrobacter, Nitrospina, Nitrococcus convert nitrites into nitrates.

Thus, the correct answer is 'Nitrosomonas and Nitrobacter.' 

Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

Which gene cluster is responsible for nitrogen fixation in bacteria?

  1. Nod, Nif, Nfx

  2. Nod, Nif, Fix

  3. Nod, Ndf, Nfx

  4. Ndx, Nif, Fix

  5. Ndx, Nif, nix
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Nitrogen fixation is a process by which nitrogen present in the atmosphere is converted into ammonia. It is essential to life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing compounds. This process is done with the help of nitrogen-fixing bacteria that have Nod, Nif and Fix gene clusters responsible for nitrogen fixation.
So the correct answer is 'Nod, Nif, Fix'.
Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

Match the columns and choose the correct option.

I II
(a) Free-living aerobic nitrogen fixers 1. Anabaena and Nostoc
(b) Anaerobic nitrogen fixers 2. Pseudomonas and Thiobacillus
(c) Nitrogen-fixing cyanobacteria 3. Nitrosomonas and Nitrosococcus
(d) Denitrifying bacteria 4. Azotobacter and Beijerinckia
(e) Nitrifying bacteria 5. Rhodospirillum

  1. a - 4, b - 5, c - 1, d - 2, e - 3

  2. a - 5, b - 4, c - 1, d - 3, e - 2

  3. a - 4, b - 5, c - 2, d - 3, e - 1

  4. a - 4, b - 3, c - 1, d - 2, e - 5

  5. a - 4, b - 5, c - 3, d - 2, e - 1
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
a) Free-living aerobic nitrogen fixers - Azotobacter and Beijernikia
b) Anaerobic nitrogen fixers - Rhodospirillum
c) Nitrogen-fixing cyanobacteria - Anabaena and Nostoc
d) Denitrifying bacteria - Pseudomonas and Thiobacillus
e) Nitrifying bacteria - Nitrosomonas and Nitosococcus
So the correct answer is 'a-4, b-5, c-1, d-2, e-3'
Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

Which of the following is the function of nitrifying bacteria?

  1. Oxidise $NH _3$ to $NO^- _3$
  2. Oxidise $NH _3$ to $NH^+ _4$
  3. Convert $NO^- _3$ to $NH _3$
  4. Convert $NO^- _3$ to $N _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Nitrifying bacteria is an aerobic bacteria that use inorganic chemicals as an energy source. They are important in the nitrogen cycle as converters of soil ammonia to nitrates by the process of oxidation.
So the correct answer is 'oxidise NH$ _3$ to NO$ _3$-'.
Multiple choice chemistry chemistry in daily life food spoilage and food preservation methods of preserving food chemicals in food

It is found in phosphorus and nitrogen

  1. inorganic impurities

  2. bacteria

  3. nutrients

  4. other microbes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Nitrogen and phosphorous are nutrints that are natural parts of aquatic ecosystems.Nitrogen is also most abundant element in the air we breath nitrogen and phosphorous support the growth of a lgee and aquatic plants,which prouide food and habbit for fish and smaller organisma that line in water.







Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

The growth of which group of bacteria will be slow in comparison to the others?

  1. Obligate aerobes

  2. Obligate anaerobes

  3. Facultative aerobes

  4. Facultative anaerobes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • The growth of Obligate aerobes will be slow in comparison to the other bacteria.
  • These group of bacteria require oxygen to grow as they cannot respire anaerobically.
  • Its growth depends on aerobic respiration and use oxygen as a terminal electron acceptor.
  • The correct answer is OPTION A.
Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

Mark the correct statement.

  1. Anaerobes grow in absence of oxygen.

  2. Aerophiles can grow in complete absence of oxygen.

  3. Aerobes can grow in absence of oxygen.

  4. Obligate anaerobes can live in the presence of abundant oxygen.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first statement is the correct one which say the organism grow with no oxygen is called as anaerobes.

So the correct option is 'Anaerobes grow in absence of oxygen'.

Multiple choice evs mud and stones soil types types of soil soil - types, uses and need for conservation

Consider the following statements:
1. Anabaena lives symbiotically with Azolla
2. Azotobacter is a free - living organism in the soil.
Which of the statements given above is/are correct?

  1. 1 only

  2. 2 only

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Anabaena, a cyanobacterium, forms a symbiotic association with the water fern Azolla, fixing atmospheric nitrogen for the plant. Azotobacter is a well-known genus of free-living diazotrophic bacteria that reside in the soil. Thus, both statements are correct.

Multiple choice evs modern agriculture agricultural practices in india different types of farming and agriculture various agricultural practices

Which is wrong among the following?

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

  2. Root nodule forming nitrogen fixers live as aerobes under free living state.

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

  4. Nitrosomonas and Nitrobacter are chemoautotrophs.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Option C is factually wrong because phosphorus is not a constituent of all proteins; while it is present in nucleic acids and certain specialized proteins or phospholipids, many standard proteins lack phosphorus entirely. The other statements regarding nitrogen fixers and chemoautotrophs are correct.