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Structure of Bacteria - 1 (Medical Entrance)

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Which of the following is a mordant that is used in gram staining of bacteria?

  1. Alcohol

  2. Safranine

  3. Crystal violet

  4. Iodine


Correct Option: D
Explanation:

Iodine is used as a mordant in gram staining. It forms a coordination complex with dye and helps in binding of dye to the cell or tissue.

Which of the following organisms requires only free oxygen to survive?

  1. Campylobacter jejuni

  2. Pseudomonas aeruginosa

  3. Clostridium tetani

  4. Streptococcus pyogenes


Correct Option: B
Explanation:

Pseudomonas aeruginosa is an obligate aerobe. It requires only free oxygen to survive.

Which of the following organisms divides in three planes?

  1. Neisseria

  2. Streptococcus pyogenes

  3. Aerococcus

  4. Staphylococcus aureus


Correct Option: D
Explanation:

Staphylococcus aureus divides in three planes in an irregular pattern, producing bunches of cocci.

Which of the following is a rod-shaped bacterium with spherical ends?

  1. Sulfolobus

  2. Bacillus anthracis

  3. Caryophanon

  4. Seliberia


Correct Option: B
Explanation:

Bacillus anthracis is a rod-shaped bacterium with spherical ends.

The direction of rotation of flagella is governed by

  1. cAMP

  2. cGMP

  3. cTMP

  4. None of the above


Correct Option: B
Explanation:

cGMP (cyclic guanine mono-phosphate) regulates the direction of rotation of flagella.

Find the odd one out.

  1. L-form

  2. Protoplast

  3. Spheroplast

  4. Eubacteria


Correct Option: D
Explanation:

Eubacteria is a bacterium of a large group that typically has simple cells with rigid cell walls and flagella for movement.

Capsular heteropolysaccharides are polymerised

  1. between the cell wall and membrane

  2. outside the cell wall

  3. inside the cytoplasm

  4. inside the nucleus


Correct Option: B
Explanation:

The capsular polysaccharides are polymerised outside the cell wall.

What is meant by PPLOs?

  1. Pleuropneumonia-life organisms

  2. Pleuropneumonia-like organisms

  3. Pleuroplasmic lysogenic organisms

  4. Pleuropneumonia L-form organisms


Correct Option: B
Explanation:

Correct Answer: Pleuropneumonia-like organisms

Which of the following are non-living ribbon-like appendages that are excreted outside a cell?

  1. Prosthecae

  2. Stalks

  3. Sheaths

  4. Fimbriae


Correct Option: B
Explanation:

Stalks are non-living ribbon-like or tubular appendages that are excreted outside the cell.

DNA is present in a bacterial cell in which of the following forms?

  1. DNA is scattered in cytoplasm.

  2. DNA is double stranded and circular.

  3. DNA is enclosed in a nucleus.

  4. There are multiple copies of DNA molecule.


Correct Option: B
Explanation:

Bacterial DNA is double stranded and circular.

The anaerobic synthesis that is found in bacteria is

  1. exergonic

  2. endergonic

  3. isothermal

  4. exothermic


Correct Option: B
Explanation:

The anaerobic synthesis that is found in bacteria is endergonic. Endergonic means absorbing energy in the form of work. Endergonic reactions are not spontaneous. By thermodynamic standards, positive work, a form of energy, is defined as moving from the surroundings (the external region) to the system (the internal region). Thus, an endergonic process is one wherein the system absorbs energy from the surroundings. Anaerobic synthesis as found in bacteria is endergonic.

D-glutamic acid is found in the capsule of

  1. Shigella flexneri

  2. Bacillus anthracis

  3. Treponema pallidum

  4. Streptococcus pneumoniae


Correct Option: B
Explanation:

The capsule of Bacillus anthracis is entirely made up of D-glutamic acid. This amino acid is rare as most of the other capsules contain L form of amino acid.

The shape-determining part of the bacterial cell wall is a polymer of:

a. N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) b. N-acetyl glucosamine and diamino pimelic acid (DAPA) c. N-acetyl muramic acid and diamino pimelic acid d. N- acetyl glucosamine, N-acetyl muramic acid and diamino pimelic acid

Which of these options is correct?

  1. Only a

  2. Only b

  3. Only c

  4. Only d


Correct Option: D
Explanation:

The shape-determining part of a cell is the cell wall. It is made up of peptidoglycan, which is a polymer of NAG, NAM and DAPA.

Which of the following statements about L-forms is incorrect?

  1. L-forms are laboratory strains of bacteria that lack cell walls.

  2. L-form cells are spheres or spheroids.

  3. L-forms stain gram-positive.

  4. Cell division in L-forms is disorganised.


Correct Option: C
Explanation:

In a gram stain test, L-forms always colour gram-negative due to the lack of a cell wall.

Which of the following is the largest bacterium in the world?

  1. Bdellovibrio

  2. Thiomargarita namibiensis

  3. Helicobacter pylori

  4. Epulospiscum fishelsoni


Correct Option: B
Explanation:

Thiomargarita namibiensis means sulphur pearl of Namibia. It is the largest bacterium in the world. It is visible to the naked eye as a speck of size 3 - 4 mm.

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