What structure allows bacteria to exchange genetic material?

Correct Answer: A

Rationale: The correct answer is A: Pili. Pili are hair-like appendages on the surface of bacteria that facilitate the exchange of genetic material through a process called conjugation. During conjugation, bacteria can transfer plasmids and other genetic material to neighboring bacteria through pili. This allows for the exchange of beneficial traits like antibiotic resistance. Choice B, Flagella, are involved in bacterial movement and not in genetic material exchange. Choice C, Endospores, are protective structures formed by bacteria in response to harsh conditions, but they are not involved in genetic material exchange. Choice D, Capsules, are protective layers around bacteria that help in adherence to surfaces and evasion of the immune system, but they do not play a role in genetic material exchange.

Correct Answer: A

Rationale: The correct answer is A: McConkey agar. Selective media selectively inhibit the growth of certain organisms while allowing others to grow. McConkey agar contains crystal violet and bile salts that inhibit the growth of Gram-positive bacteria, making it selective for Gram-negative bacteria. Choices B and C are not selective media, as they do not specifically inhibit the growth of certain types of bacteria. Choice D is incorrect as McConkey agar is indeed an example of selective media.

Correct Answer: B

Rationale: The correct answer is B because bacteria synthesize enzymes with various nature and action. This is true because bacteria can produce a wide range of enzymes to carry out different functions such as metabolism, cell wall synthesis, and nutrient acquisition. Option A is incorrect because bacteria do not synthesize identical enzyme sets due to their diverse functions. Option C is incorrect as bacteria and viruses have distinct enzyme profiles. Option D is incorrect as viruses typically have a narrower range of enzymes compared to bacteria. Therefore, the variability in enzyme types and actions produced by bacteria supports the correctness of option B.

Correct Answer: B

Rationale: The correct answer is B: prophage. In the repressed stage, a phage integrates its DNA into the host cell's chromosome, becoming a prophage. This integration allows the phage to replicate along with the host cell without causing immediate lysis. A: Antiphage is not a term used to describe a phage in a repressed stage. C: Virulent phage refers to a phage that immediately causes lysis of the host cell. D: Latent phage is not a commonly used term in this context.

Correct Answer: D

Rationale: The correct answer is D: All of the above. 1. Escherichia coli can produce endotoxin due to its lipopolysaccharide component. 2. Salmonella enterica also produces endotoxin as part of its cell wall structure. 3. Pseudomonas aeruginosa is known to produce endotoxin as well. Therefore, all of these bacteria are capable of producing endotoxin, which can trigger an excessive immune response leading to septic shock. Other choices are incorrect because they do not cover all the bacteria mentioned in the question that are capable of producing endotoxin.

Correct Answer: C

Rationale: Rationale: Both Clostridium botulinum and Clostridium tetani produce neurotoxins. Botulinum toxin affects the nervous system by blocking neurotransmitter release, causing paralysis. Tetanus toxin affects the nervous system by interfering with neurotransmitter release, leading to muscle stiffness and spasms. Therefore, Choice C is correct. Choices A and B alone are incorrect because they only mention one of the bacteria that produces a neurotoxin. Choice D is incorrect because both bacteria mentioned in Choices A and B produce neurotoxins.

Correct Answer: A

Rationale: The correct answer is A: Shigella dysenteriae. This bacteria produces the Shiga toxin, which inhibits protein synthesis by interfering with the ribosomes. Shigella dysenteriae causes severe gastrointestinal illness. The other choices, B: Clostridium botulinum, produces a neurotoxin that blocks neurotransmitter release. C: Streptococcus pneumoniae causes pneumonia and other respiratory infections. D: Mycobacterium tuberculosis causes tuberculosis by infecting the lungs. Thus, based on the toxin production and mode of action, Shigella dysenteriae is the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a flagellated protozoan with two nuclei found in the stool. It commonly causes chronic diarrhea. The other choices are incorrect because B: Entamoeba histolytica causes dysentery, not chronic diarrhea; C: Trichomonas vaginalis is a sexually transmitted infection, not typically found in stool; D: Balantidium coli is a ciliated protozoan, not flagellated.

Correct Answer: A

Rationale: The correct answer is A: Kitt-Tarozzi medium. This medium is used for the primary inoculation of suture material suspected of causing tetanus. The rationale is that Kitt-Tarozzi medium contains the necessary nutrients to support the growth of Clostridium tetani, the bacterium responsible for tetanus. This medium is selective and helps in isolating the specific pathogen from the contaminated suture material. Summary of other choices: B: Endo agar is used for the isolation of Gram-negative bacteria from clinical and non-clinical samples. C: Sabouraud agar is used for the isolation of fungi and yeast. D: Egg-yolk salt agar is used for the detection of lipase-producing bacteria, particularly Staphylococcus aureus.