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 botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

The most well studied bacterial-plant relationship is that of

  1. Cyanobacterial symbiosis with some aquatic ferms

  2. Nodulation in Sesbania stem

  3. Gall formation by Agrobacterium

  4. Growth stimulation by phosphate bacteria
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The interaction between Agrobacterium tumefaciens and plants is one of the most studied systems in plant-microbe interactions due to its ability to genetically transform plants.

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

Match the following between the name of bacteria against their activity and choose the correct combination of the options given.

   List I    List II
 A  Escherichia coli  1  Nif gene
 B  Rhizobium meliloti  2 Digestive hydrocarbons of crude oil 
 C  Bacillus thuringensis  3  Human insulin production
 D  Pseudomonas putida  4  Biocontrol of fungal disease
     5  Biodegradable insecticide

  1. A- 3, B- 1, C- 5, D- 2

  2. A- 1, B- 2, C- 3, D- 4

  3. A- 3, B- 1, C- 4, D- 2

  4. A- 1, B- 5, C- 3, D- 4
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Escherichia coli  is a Gram-negative bacteria. It plays an important role in the field of biotechnology, where it has served as a host organism in recombinant DNA technology. The bacterium can be grown and cultured easily. One of the first useful application of recombinant technology was the manipulation of E.coli to produce human insulin.
Rhizobium meliloti is a Gram-negative, nitrogen-fixing bacterium. It is a symbiotic bacteria lives in the association with legumes. The bacteria possesses nif genes, responsible for the nitrogen fixation.
Bacillus thuringensis is a soil dwelling bacteria. It has been used as a biological pesticide. During spore formation, the bacteria produces crystal proteins called as endotoxins which have insecticidal action.
Crude oil is a complex mixture of hydrocarbons. Several strains of bacterium Pseudomonas putida were known to produce enzymes that degrade these hydrocarbons, i.e., the bacteria ate the hydrocarbons, nourishing themselves and reproducing.

So, the correct answer is option A.

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

The two bacteria found to be very useful in genetic engineering experiments are

  1. Nitrosomonas and Klebsiella

  2. Escherichia and Agrobacterium

  3. Nitrobacter and Azotobacter

  4. Rhizobium and Diplococcus
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bacteria like E. coli have very short generation times. Combined with the high copy number of plasmid they produce, they duplicate the plasmid with pretty good fidelity for other uses. Agrobacterium tumefaciens is capable of transferring a particular DNA segment of the tumour-inducing (Ti) plasmid into the nucleus of infected cells where it is subsequently integrated into the host genome. 

Multiple choice botany bacteria bacteria - friend and foe useful and harmful bacteria bacteria; benefits and harmful effects

The bacterium, Pseudomonas is useful because of its ability to 

  1. Transfer genes from one plant to another.

  2. Decompose a variety of organic compounds.

  3. Fix atmospheric nitrogen in the soil.

  4. Produce a wide variety of antibiotics.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The genus Pseudomonas are adapted to very different environments. This capability to thrive in various habitats coincides with an enormous metabolic capacity of this genus to use recalcitrant compounds as carbon source as well as to produce a wide range of secondary metabolites and biopolymers. Environmental applications of various Pseudomonas species in biodegradation of recalcitrant pollutants as well as biocontrol agents in plant growth promotion is very common.

Multiple choice zoology diversity in living world hemichordata phylum hemichordata chordates and hemichordates

Choose the correct answer from the alternatives given.
Which of the following is free-living bacteria responsible for nitrogen fixation?

  1. Pseudomonas

  2. Rhodospirillum

  3. Azotobacter

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Non-symbiotic bacteria in the soil and symbiotic bacteria that live in the roots of plants are capable of nitrogen fixation. Bacteria in the genera Clostridium and Azotobacter are non-symbiotic nitrogen-fixing bacteria, while those in the genus Rhizobium are symbiotic bacteria. Pseudomonas species fixes nitrogen under microaerobic conditions in the free-living state and colonizes rice endophytically. Nitrogen fixation in phototrophic bacteria has been found in Rhodospirillum rubrum. 

So, the correct option is, 'All of these'.

Multiple choice biology economic importance of bacteria and fungi common diseases in humans epidemics transmission of diseases

Ray fungi as diazotrophs are

  1. Streptomyces and Mycoplasma

  2. Gram negative monerans and symbiotically associated with Xanthomonas

  3. Gram positive monerans and symbiotically associated with Alnus
  4. Chemoautotrophic $ { N } _{ 2} $ - fixer
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Actinomyces species of bacteria form colonies that have fungus like branched networks of hyphae and are therefore also known as ray fungus. They are gram positive and a few species of nitrogen fixing bacteria live in symbiosis with actinorhizal plants of the genus Alnus. 

So, the correct option is 'Gram-positive monerans and symbiotically associated with Alnus'.

Multiple choice bio-chemistry unit of living - cell eukaryotic cell kinds of cell introduction to eukaryotic cell

How many of following statements are not true?
1) Some unicellular Eukaryotes are capable of fixing Nitrogen
2) Infection thread contains an oxygen scavenger called leg-haemoglobin
3) Successful infection of the root hair causes it to curl
4) Ureides have particularly high nitrogen to carbon ratio 

  1. One

  2. Two

  3. Three

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

Statement 1 is false (no eukaryotes fix nitrogen). Statements 2, 3, and 4 are correct. Since only one statement is false, the answer 'One' is correct.

Multiple choice biology movement and locomotion in living organisms movements in plants coordination in plants tropic and nastic movements in plants

Pneumatophores are 

  1. Negatively geotropic

  2. Positively geotropic

  3. Negatively phototropic

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

Pnuematophores are called as breathing roots. These are found in mangrove trees. These are the modifications in root which grows in the same direction as that of shoot. Thus, they are negatively geotropic as well as positively phototrophic.

Multiple choice biology movement and locomotion in living organisms movements in plants coordination in plants tropic and nastic movements in plants

Pneumatophore are

  1. Positively geotropic

  2. Negative phototropic

  3. Negatively geotropic

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

Pneumatophores are negatively geotropic roots found in mangroves. They have pores for gaseous exchange. These pores are important because the soil is waterlogged and there is deficiency of air in the soil.

Thus, the correct answer is option C.

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

Which of the following statements is/are incorrect ?
(i) Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial habitats.
(ii) Anabaena, Nostoc and Oscillatoria are photosynthetic $N _2$ - fixing cyanobacteria.
(iii) Tolypothrix (BGA) can increase rice production by about 20%.
(iv) BGA add organic matter to the soil and increase its fertility.
(v) In our country, fertilizers are not available commercially in the markets for farmers.

  1. (v) Only

  2. (iv) Only

  3. (iii) Only

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Biofertilizers are available commercially in our country for farmers.

So, the correct option is '(v) Only'

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

Which one of the following microorganisms forms a symbiotic association with plants and helps them in their nutrition?

  1. Glomus

  2. Azotobacter

  3. Klebsielfa

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

Several fungi are known to form symbiotic associations with plants, i.e., mycorrhiza. The most common fungal partners of mycorrhiza are Glomus species.

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

Study the following statements and select the correct ones.


(i) Methanogens are archaebacteria that produce methane in marshy areas.
(ii) Nostoc is a filamentous blue-green alga which fixes atmospheric nitrogen.
(iii) Many members of the genus Glomus form mycorrhiza.

  1. (i) and (ii)

  2. (i) and (iii)

  3. (ii) and (iii)

  4. (i), (ii) and (iii)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
1. Methanogens are archaebacteria belong to the domain of archaea, commonly found in wet, marshy areas,  They produce methane gas.
2. Nostoc is the filamentous blue-green alga. They form gelatin body which contains trichomes.
3. Glomus and it's all species form symbiotic relationships (mycorrhizas) with plant roots. 
So the correct answer is option D.