Free Kingdom Prokaryotae MCQs with Answers

481. The size of Spirochete is approximately?

• A. 0.75-1.25 μm
• B. 100-200 nm
• C. 0.1-600 μm
• D. 500 μm

Explanation: The correct answer is Option D: 500 μm. Spirochetes are known for their unique spiral shape and can vary significantly in size. While most bacteria are much smaller, some spirochetes can indeed reach lengths of up to 500 micrometers, making them among the largest known bacteria. Option A (0.75-1.25 μm) is more typical of many smaller bacterial species. Option B (100-200 nm) is incorrect as it falls within the size range of viruses, not bacteria. Option C (0.1-600 μm) is overly broad and not specific to spirochetes.

482. Which of the following bacteria is equal to the size of hyphen?

• A. Epulopiscium fishelsoni
• B. Pseudomonas aeruginosa
• C. Escherichia coli
• D. Streptococcus pneumoniae

Explanation: The correct answer is Epulopiscium fishelsoni, which is one of the largest known bacteria, reaching lengths up to 0.5 millimeters, approximately the size of a hyphen. This makes it unique among bacteria, which are typically much smaller. Pseudomonas aeruginosa, Escherichia coli, and Streptococcus pneumoniae are all much smaller, generally in the range of 1-2 micrometers in size, and thus do not match the size comparison to a hyphen.

483. What is the main role of bacteria?

• A. CO2 cycle
• B. Nitrogen cycle
• C. Phosphorus cycle
• D. All of the above

Explanation: Bacteria are indispensable in various biogeochemical cycles. In the carbon cycle, they decompose organic matter, releasing carbon dioxide. In the nitrogen cycle, they perform nitrogen fixation, ammonification, and denitrification, all crucial for nitrogen availability. In the phosphorus cycle, they transform phosphorus into forms usable by plants. Therefore, the correct answer is 'All of the above' as bacteria contribute to all these cycles significantly. The other options are too narrow, focusing on only one specific role.

484. DNA replication in bacteria occurs:

• A. Within nucleolus
• B. Prior to fission
• C. Just before transcription
• D. During S phase

Explanation: In bacteria, DNA replication occurs just prior to binary fission, ensuring that each daughter cell receives a complete set of genetic material. This is a crucial step for bacterial reproduction, as it allows for genetic continuity.

485. Why is a capsule advantageous to a bacterium?

• A. It protects the bacterium from desiccation
• B. Provides pathogenicity to bacteria
• C. It allows bacterium to "hide" from host's immune system
• D. It allows the bacterium to attach to the surface
• E. All

Explanation: A bacterial capsule is advantageous to a bacterium, particularly in terms of pathogenicity, for the following reasons:1. **It protects the bacterium from desiccation:** This protective capsule helps pathogens survive outside of a host. When a bacterium is expelled from a host, it may face harsh environmental conditions, including drying out (desiccation). The capsule acts as a shield, retaining moisture and preventing the bacterium from drying up, enhancing its ability to persist in the environment and potentially infect new hosts.2. **It allows the bacterium to "hide" from the host's immune system:** Pathogenic bacteria often possess capsules composed of materials that are not easily recognized by the host's immune system. This camouflage effect makes it difficult for immune cells to detect and eliminate the bacterium. By "hiding" from the immune system, the bacterium can establish infections and continue to cause disease.3. **It allows the bacterium to attach to a surface:** Bacterial capsules can aid in adhesion to host tissues and surfaces. This is a critical step in the pathogenic process. For instance, many pathogenic bacteria need to adhere to host cells or tissues to initiate an infection. The capsule can facilitate this attachment, allowing the bacterium to colonize and establish infections in the host.In the context of pathogenicity, these advantages of a bacterial capsule contribute to the bacterium's ability to evade host defenses, survive in various environments, and initiate infections within the host's body.

486. Which of the following is false about conjugation?

• A. It forms a bridge between two bacterial cells
• B. It involves the transport of genetic material via vectors
• C. It is a form of sexual reproduction
• D. None of these

Explanation: Bacterial conjugation is a mechanism of horizontal gene transfer where genetic material, typically plasmid DNA, is directly transferred between two bacterial cells via a conjugation bridge. Option A is true because the formation of this bridge is essential for conjugation. Option B is the correct answer because vectors are not involved in this process. Option C is also true, as the process introduces genetic diversity similar to sexual reproduction. Option D is incorrect, as Option B provides a false statement about conjugation.

487. Curve screw shaped bacteria are known:

• A. Cocci
• B. Bacilli
• C. Spirilla
• D. None of these

Explanation: Spirilla bacteria are also termed curve screw shaped.

488. In many bacteria cell wall is enclosed within a slime capsule made up of:

• A. Polysaccharides
• B. Cellulose
• C. Amino Acids
• D. Proteins

Explanation: A bacteria consists of glycocalyx- the outermost covering of a bacteria, that exists in two forms i.e., capsule and slime. Glycocalyx is made up of polysaccharides in some cases proteins are also present.

489. The bacteria can cope unfavourable condition by producing?

• A. Mesosomes
• B. Zygospores
• C. Endospores
• D. Cysts

Explanation: Endospores are dormant bodies that are capable of surviving for longer periods and are resistant to higher temperatures and UV radiations. They stay dormant until they meet the necessary conditions to germinate.

490. Apparently which bacteria are more resistant to antibiotics?

• A. Gram positive bacteria
• B. Gram negative bacteria
• C. Both Gram positive & negative
• D. None of these

Explanation: In Gram-negative bacteria, periplasmic space - the space between the peptidoglycan layer of the cell wall and cell membrane which is the site of enzymes that degrade antibiotics.