Free Kingdom Prokaryotae MCQs with Answers

471. Which of the following statement is incorrect regarding germ theory of diseases postulated by Robert Koch?

• A. A specific organism can always be found in association with a given disease
• B. The organism can be isolated and grown in pure culture in the laboratories
• C. It is possible to recover the organism in pure culture from the experimentally infected animals.
• D. The pure culture cannot produce the disease when inoculated into susceptible animal.

Explanation: Koch's fourth postulate states that the pure culture of the isolated microorganism should be capable of reproducing the disease when inoculated into a healthy, susceptible animal. This step is essential to establish a cause-and-effect relationship between the microorganism and the disease. If the cultured microorganism does not produce the disease when introduced into a healthy animal, it raises doubts about its role in causing the disease.

472. Example of bacteria requiring low concentration of oxygen is:

• A. Spirochete
• B. Escherichia
• C. Pseudomonas
• D. Campylobacter

Explanation: Campylobacter is a genus of bacteria that includes several species, such as Campylobacter jejuni and Campylobacter coli. Campylobacter is microaerophilic, which means it requires low concentrations of oxygen (typically 5-10% oxygen) to grow optimally. It is not strictly anaerobic like some other bacteria but does not grow well in the presence of normal atmospheric levels of oxygen (around 20%). Campylobacter is commonly found in the intestines of birds and mammals and is a common cause of foodborne illnesses in humans.

473. Robert Koch discovered bacteria that cause:

• A. Tuberculosis and Typhoid
• B. Tuberculosis and Cholera
• C. Tuberculosis and Measles
• D. All of above

Explanation: Robert Koch discovered the bacteria that cause several diseases, including tuberculosis and cholera.

474. As we know certain species of bacteria produce spores, these all are the characterstics of a spore except:

• A. Spores can be located outside the vegetative cells
• B. Spores exhibit resistance to harsh environmental conditions
• C. Spores can form within vegetative cells
• D. Spores can never germinate into vegetative cells

Explanation: Bacterial spores, especially endospores, are highly resistant structures formed by certain bacteria such as those in the genera Bacillus and Clostridium. These spores can survive in harsh conditions by entering a dormant state. When conditions improve, they can germinate back into vegetative cells. The statement that spores 'can never germinate into vegetative cells' is incorrect, making it the correct choice in this context. The other options describe accurate characteristics of bacterial spores, thereby making them incorrect choices.

475. These are hollow, non-helical, filamentous appendages:

• A. Flagella
• B. Pili
• C. Trichomes
• D. Plasmids

Explanation: The correct answer is Pili. Pili are hollow, non-helical, filamentous structures found on the surface of many bacteria. They play critical roles in bacterial conjugation, a process of genetic exchange, and in the attachment of bacteria to different surfaces, which can be crucial for colonization and infection. Unlike flagella, which are helical and involved in motility, pili do not contribute to bacterial movement. Trichomes and plasmids are unrelated to the description provided, as trichomes are not hollow, non-helical bacterial appendages, and plasmids are DNA molecules, not structural appendages.

476. Pili are hollow appendages in bacteria that are used for:

• A. Motility
• B. Conjugation
• C. Chemical detection
• D. Attachment to surfaces

Explanation: The correct answer is Conjugation. Pili are specialized structures in bacteria used to connect two cells and facilitate the transfer of genetic material, a process known as conjugation. This enhances genetic diversity and can confer beneficial traits such as antibiotic resistance.

477. True bacteria are termed as:

• A. Eubacteria
• B. Archaeobacteria
• C. Cyanobacteria
• D. None of the above

Explanation: Eubacteria, or true bacteria, are a major group of prokaryotic microorganisms characterized by their peptidoglycan-containing cell walls and their adaptability to diverse environments. They are distinct from archaeobacteria, which are prokaryotes with unique genetic and biochemical features found in extreme habitats. Cyanobacteria are a subgroup of eubacteria known for photosynthesis but do not encompass the entire true bacteria group. Therefore, the correct answer is Eubacteria.

478. Which of the following is heat resistant organelle?

• A. Spores
• B. Cysts
• C. Granules
• D. All of the Above

Explanation: Spores are the most heat-resistant structures formed by certain bacteria, allowing them to endure extreme environmental conditions, including high temperatures, radiation, and dehydration. This adaptation ensures bacterial survival until conditions become favorable again. In contrast, cysts provide protection against some unfavorable conditions but do not offer the same level of heat resistance as spores. Granules are used for nutrient storage and do not confer heat resistance. Therefore, option A is the correct choice, as only spores are specifically designed to be heat resistant.

479. Which part of bacteria is most delicate and can damage bacterial cell immediately?

• A. Cell wall
• B. Cell membrane
• C. Slime layer
• D. Capsule

Explanation: The cell membrane is the most delicate part of the bacterial cell because it is thin and flexible. It plays a crucial role in protecting the cytoplasm and regulating the transport of substances into and out of the cell. Damage to the cell membrane can lead to the immediate death of the bacteria. In contrast, the cell wall, slime layer, and capsule are more robust structures that provide protection and support, but they are not as critical to the cell's immediate survival as the cell membrane.

480. Cyanobacteria are related to eukaryotes in having:

• A. PS-I
• B. PS-II
• C. Both A and B
• D. None

Explanation: The correct answer is Option C: Both A and B. Cyanobacteria and eukaryotes share Photosystem I (PSI) and Photosystem II (PSII) as part of their photosynthetic machinery. These photosystems are essential for converting light energy into chemical energy during photosynthesis. PSI captures light energy to facilitate the transfer of electrons, while PSII uses light energy to extract electrons from water, releasing oxygen. Options A and B are incorrect because they only mention one of the photosystems, whereas both are necessary for the full range of photosynthetic functions shared between cyanobacteria and eukaryotes. Option D is incorrect because cyanobacteria do possess these photosystems.