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 botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Which of the given statements are correct?
(i) Bacillus subtilis is a Gram(+) bacteria
(ii) Escherichia coli is a Gram (-) bacteria
(iii) Washing of the Gram's stain in Gram (-) bacteria is due to high lipid content of the cell wall, which gets dissolved in organic solvents like acetone

  1. (i) and (ii)

  2. (ii) and (iii)

  3. (i) and (iii)

  4. (i), (ii) and (iii)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bacteria can be classified into two groups based upon reaction bacteria to Gram's stain (Christian Gram, 1884. Bacteria are first stained with weakly alkaline solution of crystal violet and then treated with 0.5% iodine solution. This is followed by washing with water and then with alcohol or acetone. Bacteria which retain blue or purple colour are known as Gram (+) bacteria (e.g Bacillus subtilis). Bacteria which do not retain stain and become colourless are called Gram (-) bacteria (e.g. Escherichia coli). Washing of the stain in Gram (- ve) bacteria is due to high lipid content of their cell wall which gets dissolved in organic solvents like acetone. So, the correct answer is '(i), (ii) and (iii)'.

Multiple choice botany living world and classification of microbes gram staining microbiology: organisms in industry cell wall and cell membrane

Mucopeptide of cell wall is more in

  1. Gram-positive bacteria

  2. Gram-negative bacteria

  3. Cyanobacteria

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

Cell wall of Gram +ve bacteria is made up of peptidoglycans (mucopeptide). Mucopeptide form about 50% of component of cell wall. Cell wall of Gram -ve bacteria is made up of single layer of peptidoglycans.

Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Bacteria which retain purple colour after staining with gram stain is

  1. Gram +ve

  2. Gram -ve

  3. Trichous

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

Gram staining procedure is based on the principle of the ability of microorganisms to retain color of the stains used during the gram staining process. Gram-positive bacteria retain purple color after staining. They are not decolorized by treatment with alcohol. Whereas gram-negative bacteria are decolorized by the alcohol and lose purple color. When again stained with the second stain, they retain pink color. This major difference is due to the difference in the cell wall component of both the bacteria. Gram-negative bacteria contain additional peptidoglycan layer and a thin layer of LPS layer. 

Thus, the correct answer is 'Gram +ve.'

Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Gram $(-)$ve bacteria possess peptidoglycan and an extra layer of

  1. Protein

  2. Lipoprotein

  3. Lipopolysaccharide

  4. Lipid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Both Gram negative and Gram positive bacteria have a peptidoglycan layer in the cell wall. Peptidoglycan is also called as mucopeptide. It is a polymer that is made up of sugars and amino acids. Gram positive bacteria have thick layer of peptidoglycan. However, Gram negative bacteria have thin layer of peptidoglycan. Apart from this, Gram negative bacteria have outer wall made up of lipopolysaccharide. 
Thus, the correct answer is 'Lipopolysaccharide.'
Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

The periplasmic space of the Gram$(-)$ bacteria consists of

  1. Lipoprotein

  2. Mucopeptide

  3. Chromoprotein

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

Both Gram negative and Gram positive bacteria have a peptidoglycan layer in the cell wall. The peptidoglycan in Gram negative bacteria is present in the periplasmic space. Apart from this, Gram negative bacteria have an outer wall made up of lipopolysaccharide. Peptidoglycan is also called as mucopeptide. It is a polymer that is made up of sugars and amino acids. 

Thus, the correct answer is 'Mucopeptide.'

Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

What is correct about Escherichia coli and Rhizobium japonicum?

  1. E.coli is Gram - and R. japonicum Gram +

  2. Both Gram +

  3. Both Gram -

  4. E.coli Gram + and R. japonicum Gram -
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both Escherichia coli and Rhizobium japonicum are Gram-negative bacteria, meaning they have a thin peptidoglycan layer and an outer membrane.

Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Gram negative bacteria detect and respond to chemicals through the receptors in

  1. Muramic acid

  2. Lipopolysaccharide

  3. Porins

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

It holds receptor molecules that help bacteria detect and respond to chemicals in their surroundings

So, the correct answer is 'lipopolysaccharides'

Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Identify the Gram $(-)$ bacterium

  1. Streptomyces coelicolor

  2. Escherichia coli

  3. Ampycolatopsis orientalis

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

Gram-negative bacteria are bacteria that do not retain the crystal violet stain during gram-staining procedure. Gram positive bacteria are bacteria that retain the crystal violet stain during gram staining procedure. Examples of Gram negative bacteria include Escherichia coli, Helicobacter pylori. Examples of Gram positive bacteria include Bacillus subtilis, Streptomyces coelicolor, Streptomyces orientalis (Ampycolatopsis orientalis).

Thus, the correct answer is 'Escherichia coli.'

Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Bacteria were grown in a medium containing heavy isotope of nitrogen (N15) for many generations and all their DNA contained many heavy nitrogen only. A bacterium of this type was transferred to normal medium and allowed to duplicate. After two divisions of heavy DNA is likely to be that

  1. Only one daughter cell will have heavy DNA

  2. Two daughter cells have normal DNA and other two

  3. All daughter cells have heavy DNA

  4. Half daughter cells have heavy DNA and other half have normal DNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

After two divisions, four bacterial cells are formed in which two daughter bacterial cells have normal DNA and other two have both normal and heavy DNA because DNA replicates by semiconservative method in bacteria.

Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Some gram $-$ve bacteria have peptidoglycan and an extra layer of.

  1. Lipo polysaccharide

  2. Lipo-protein

  3. Protein

  4. Both A and C
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Both Gram negative and Gram positive bacteria have a peptidoglycan layer in the cell wall. Peptidoglycan is also called as mucopeptide. It is a polymer that is made up of sugars and amino acids. Gram positive bacteria have thick layer of peptidoglycan. However, Gram negative bacteria have thin layer of peptidoglycan. Apart from this, Gram negative bacteria have outer wall made up of lipopolysaccharide.
Thus, the correct answer is 'Lipo polysaccharide.'
Multiple choice botany option b: biotechnology and bioinformatics gram staining microbiology: organisms in industry cell wall and cell membrane

Select the correct option:

Which of the given statements are correct?
(i) Bacillus subtilis is a Gram $(+)$ bacteria.
(ii) Escherichia coli is a Gram $(-)$ bacteria.
(iii) Washing of the Gram's stain in Gram $(-)$ bacteria is due to high lipid content of the cell wall, which gets dissolved in organic solvent like acetone.

  1. (i) and (ii)

  2. (ii) and (iii)

  3. (i) and (iii)

  4. (i), (ii) and (iii)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bacteria can be classified into two groups based upon reaction of bacteria to Gram's stain (Christian Gram, $1884$). Bacteria are first stained with weakly alkaline solution of crystal violet and then treated with $0.5$% iodine solution. This is followed by washing with water and then with alcohol or acetone. 

Bacteria which retain blue or purple colour are known as Gram $(+)$ bacteria (e.g., Bacillus subtilis). 
Bacteria which do not retain stain and become colourless are called Gram $(-)$ bacteria (e.g., Escherichia coli). Washing of the stain in Gram $(-ve)$ bacteria is due to high lipid content of their cell wall which gets dissolved in organic solvents like acetone.
So, the correct answer is '(i), (ii) and (iii)'.

Multiple choice botany living world and classification of microbes gram staining microbiology: organisms in industry cell wall and cell membrane

The Gram negative bacteria detect and respond to chemical in their surrounding by

  1. Lipopolysaccharide

  2. Muramic acid

  3. Porins

  4. Volutin granules

  5. Mesosomes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a decolourizer such as alcohol or acetone is added, it interacts with the lipids of the cell membrane. A Gram-negative cell loses its outer lipopolysaccharide membrane and the inner peptidoglycan layer is left exposed. The crystal violet complexes are washed from the Gram-negative cell along with the outer membrane.

Multiple choice biology soil : our life soil properties soil - properties basics of soil pollution

An example of nitrogen fixing bacteria in the soil

  1. Rhizobium

  2. Nostoc

  3. Azotobacter

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

Azotobacter is a well-known free-living nitrogen-fixing bacterium found in soil. Rhizobium is also a nitrogen fixer, but it is symbiotic (living in root nodules), while Nitrobacter is involved in nitrification, not nitrogen fixation.

Multiple choice botany the living world archaebacteria the three domains of life classification of microbes

Archarbacteria with purple coloured pigment in cell membrane :

  1. Can survive in extreme saline conditions.

  2. Are chemoautotrophs

  3. Can use light energy to synthesize ATP

  4. Both (A) and (C)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Answer is option D i.e. "Both (A) and (C)"
Archarbacteria are salt loving bacteria that can live in strong salt solutions. Hence they are also called halophiles. In presence of strong sunlight they develop a purple colored pigmented membrane to utilize light energy producing ATP.

Multiple choice botany the living world archaebacteria the three domains of life classification of microbes

Study the following statements and select the correct ones.
(i) Methanogens are archaebacteria which 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
D Correct answer
Explanation
Methanogens are archaebacteria which produce methane in marshy areas. Nostoc is a filamentous blue-green alga which fixes atmospheric nitrogen. Many members of the genus Glomus form endomycorrhiza.
So, the correct option is '(i), (ii) and (iii)'