Free Kingdom Prokaryotae MCQs with Answers

251. The incubation period of Syphilis is:

• A. 1-2 weeks
• B. 2-3 weeks
• C. 3-4 weeks
• D. 7 days

Explanation: The incubation period of syphilis, which is the time between exposure to the bacteria (Treponema pallidum) and the appearance of symptoms, typically ranges from 2 to 3 weeks. However, it can vary from 10 to 90 days, with an average of around 21 days.

252. Which component is present only in the cell wall of Gram-positive bacteria but NOT in Gram-negative bacteria?

• A. Teichoic acids
• B. Lipids
• C. Peptidoglycan
• D. Periplasmic space

Explanation: Teichoic acids are unique components found only in the cell walls of Gram-positive bacteria. They are acidic, phosphate-containing polysaccharides that play a crucial role in maintaining the structural integrity of the cell wall and providing a negative charge to the cell surface.Gram-positive bacteria have a thick peptidoglycan layer (20-80 nanometers) and a teichoic acid layer, whereas Gram-negative bacteria have a thinner peptidoglycan layer (2-3 nanometers) and an outer membrane containing lipopolysaccharides.

253. The cells of the non virulent strain of Streptococcus pneumonia are:

• A. Capsulated and S-Type
• B. Non-capsulated and S-Type
• C. Capsulated and R-Type
• D. Non-capsulated and R-Type

Explanation: Streptococcus pneumoniae strains are classified into two main types based on their capsule:- S-type (Smooth-type): Capsulated, virulent strains with a smooth colony morphology.- R-type (Rough-type): Non-capsulated, non-virulent strains with a rough colony morphology.The capsule is a layer of polysaccharides surrounding the bacterial cell wall, which helps protect the bacteria from phagocytosis and is a key virulence factor. Non-virulent strains lack this capsule, making them more susceptible to host immune responses.

254. An additional covering surrounds the cell wall of some bacteria that either prevents the bacteria from being phagocytosed by host cells or helps them to make biofilm.Which of the following term is used for this covering?

• A. Capsule
• B. Slime
• C. Glycocalyx
• D. Spore

Explanation: The capsule is an additional covering that surrounds the cell wall of some bacteria, providing protection against:- Phagocytosis (engulfment by host cells)- Desiccation (drying out)- Antibiotics and other antimicrobial agentsThe capsule is composed of polysaccharides (complex sugars) and can be found in both Gram-positive and Gram-negative bacteria.

255. Which mode of genetic exchange between bacteria involves cell-to-cell contact between the bacterial cells?

• A. Transduction
• B. Transformation
• C. Conjugation
• D. Both a and b

Explanation: Conjugation is the process of genetic exchange between bacteria that involves direct cell-to-cell contact between the bacterial cells. It requires a specialized structure called a conjugation pilus, which allows the cells to attach and transfer DNA from one cell to another.

256. Which of the following is a prokaryote?

• A. Protista
• B. E.coli
• C. Amoeba
• D. Fungi

Explanation: E. coli (Escherichia coli) is a type of bacteria, which is a prokaryote. Prokaryotes are single-celled organisms that lack a true nucleus and other membrane-bound organelles. They have a simple cell structure and are typically small in size.

257. Endospore formation is _

• A. A reproductive process
• B. A vegetative process
• C. Can be reproductive or vegetative depending on the conditions
• D. Is related to invading host cells

Explanation: Endospore formation is a survival mechanism used by certain bacteria, such as Bacillus and Clostridium species, to withstand harsh environmental conditions like high temperatures, radiation, and chemicals. During endospore formation, the bacterial cell undergoes a series of changes to produce a highly resistant, dormant cell called an endospore.Endospore formation is a vegetative process because it:- Involves the transformation of a single cell into a highly resistant form- Is not directly involved in reproduction or the production of new cells- Helps the bacterium survive adverse conditions, allowing it to remain dormant until favorable conditions return

258. Which one is a chemotherapeutic agent to destroy and stop the growth of bacteria?

• A. Phenol
• B. Spirit
• C. Pencilin
• D. Sulphuric Acid

Explanation: Correct, as it is an antibiotic that inhibits bacterial cell wall synthesis.

259. In prokaryotic cells, which one of the following organelles is present?

• A. Mitochondria
• B. Nucleus
• C. Golgi apparatus
• D. Ribosomes

Explanation: Ribosomes - Correct. Prokaryotic cells have ribosomes (70S type) for protein synthesis, though they are smaller than eukaryotic ribosomes.

260. Phycocyanin is a pigment present in cyanobacteria. Phycocyanin is of _ color.

• A. Green
• B. Blue
• C. Yellow
• D. Red

Explanation: Blue - Correct. Phycocyanin is a blue pigment found in cyanobacteria that assists in photosynthesis.