Free Kingdom Prokaryotae MCQs with Answers

271. Which bacteria are called scavengers of earth?

• A. Parasitic bacteria
• B. Saprophytic bacteria
• C. Symbiotic bacteria
• D. Photosynthetic bacteria

Explanation: Saprophytic bacteria are called scavengers of earth because these bacteria decompose dead organic matter and obtain nutrients from decaying organic material, playing a viral role in recycling nutrients in the environment. So, option B is the most accurate answer.

272. In Gram -ve bacteria, the peptidoglycan layer is:

• A. Condensed
• B. Thick
• C. Moderate
• D. Thin
• E. Entangled

Explanation: In gram-negative bacteria, the peptidoglycan layer is relatively thin compared to gram-positive bacteria.

273. The type of bacteria which oxidize CO into CO2 is:

• A. Norcardia salmonicolor
• B. Hydrogenomonas
• C. Pseudomonas
• D. Thiobacillus
• E. Azobacter

Explanation: The correct answer is Pseudomonas because some species within this genus have the unique ability to oxidize carbon monoxide (CO) as a source of energy, facilitating their survival in environments where CO is present. The other options are incorrect because:Norcardia salmonicolor is involved in the degradation of organic compounds, not CO oxidation.Hydrogenomonas utilizes hydrogen rather than carbon monoxide.Thiobacillus is associated with sulfur and carbon cycles but does not oxidize CO.Azobacter is known for nitrogen fixation and does not rely on carbon monoxide for energy.Thus, Pseudomonas stands out as the only correct option in this context.

274. Which of the following accurately describes Helicobacter pylori?

• A. Flagellated rod-shaped bacterium
• B. Flagellated chain bacterium
• C. Flagellated spiral-shaped bacterium
• D. Non-flagellated spiral-shaped bacterium
• E. Non-flagellated rod-shaped bacterium

Explanation: Helicobacter pylori is a flagellated spiral-shaped bacterium. Its spiral shape and flagella help it move through the mucus lining of the stomach, contributing to its pathogenicity. The other options are incorrect because they do not accurately describe both the flagellation and the spiral shape of H. pylori. Options describing it as rod-shaped or non-flagellated do not match its known scientific characteristics.

275. Respiration in Pseudomonas bacteria is:

• A. Aerobic
• B. Anaerobic
• C. Facultative
• D. Microaerophill

Explanation: Aerobic organisms are microorganisms and other living beings that require oxygen for their survival and growth. They use oxygen in the process of aerobic respiration, a metabolic pathway that generates energy efficiently by oxidizing organic substrates.

276. Bacterial genome becomes diploid:

• A. After fertilization of gametes
• B. Before spore formation
• C. During binary fission
• D. After binary fission

Explanation: The circular bacterial genome is replicated. The process begins at the origin of replication, where the DNA unwinds and new complementary strands are synthesized, resulting in two identical copies of the genome.

277. One of the following is CORRECT regarding flagella:

• A. Made up of microfilaments
• B. Contains centriole
• C. Originates from basal bodies
• D. They are immotile

Explanation: Flagella originate from basal bodies, which are protein structures located at the base of these appendages. Basal bodies serve as microtubule-organizing centers, anchoring and initiating the assembly of the axoneme-the core structural component of flagella. Structurally similar to centrioles, basal bodies consist of nine peripheral microtubule triplets arranged in a cylindrical pattern. In cells destined to have a single primary cilium, the mother centriole differentiates into the basal body upon entry into the G1 phase or during quiescence. In multiciliated cells, basal bodies can be generated de novo from a specialized structure called the deuterosome. This transformation is crucial for the proper formation and function of flagella, facilitating cell motility and sensory functions.

278. Which option is CORRECT about endospore?

• A. Has a short dormant period
• B. Contains moisture for survival
• C. Metabolically active
• D. Endures extreme condition

Explanation: Endospores are incredibly resilient to extreme environmental conditions, including high temperatures, desiccation, radiation, and chemical disinfectants. This resistance is due to their tough outer layers.

279. Bacteria divide at exponential rate during which growth phase!

• A. Lag
• B. Log
• C. Stationary
• D. Decline

Explanation: In this phase, bacteria divide rapidly by binary fission, where each cell splits into two identical daughter cells. The population grows exponentially, doubling at a constant rate. This is the period of maximum growth and optimal conditions for cell division.

280. Which one of the following organelles is ONLY present in Cyanobacteria?

• A. Heterocyst
• B. Lysosomes
• C. Mitochondria
• D. Ribosomes

Explanation: Heterocysts are specialized cells found in certain filamentous cyanobacteria (blue-green algae) that play a critical role in nitrogen fixation.