... structure of bacteria are:

Correct Answer: D

Rationale: The correct answer is D: Cytoplasmic membrane - essential. The cytoplasmic membrane is a crucial structure in bacteria as it regulates the passage of substances in and out of the cell, provides structural support, and is essential for maintaining cell integrity. Without a functional cytoplasmic membrane, bacteria would not be able to survive. A: Nucleus is incorrect because bacteria do not have a true nucleus. B: Capsule - non-essential is incorrect because while the capsule provides protection and helps in adherence, it is not essential for bacterial survival. C: Mitochondria is incorrect because bacteria do not have mitochondria; they generate energy through other mechanisms. In summary, the cytoplasmic membrane is essential for bacterial survival, making it the correct choice among the options provided.

Correct Answer: A

Rationale: Step 1: Ziehl-Neelsen staining is a type of acid-fast staining used to detect acid-resistant bacteria like Mycobacterium species. Step 2: Acid-resistant bacteria have a high lipid content in their cell walls, making them resist decolorization with acid-alcohol. Step 3: Mycobacterium species, such as M. tuberculosis and M. leprae, are examples of acid-resistant bacteria. Step 4: Spores are not typically stained using Ziehl-Neelsen staining, making choice B incorrect. Step 5: Metachromatic bodies are stained using specific techniques like Albert's stain, not Ziehl-Neelsen staining, making choice C incorrect. Summary: Ziehl-Neelsen staining is specifically used for acid-resistant bacteria detection, making choice A the correct answer. Choices B and C are incorrect as they do not align with the purpose of Ziehl-Neelsen staining. Choice D is incorrect as Ziehl

Correct Answer: A

Rationale: The correct answer is A: Listeria monocytogenes. This pathogen can cross the placenta and infect the fetus, leading to serious complications. Listeria can cause miscarriage, stillbirth, or severe neonatal infections. Staphylococcus aureus and Corynebacterium diphtheriae do not typically cross the placenta. Choice D is incorrect because Listeria monocytogenes can indeed be transmitted through the placenta, unlike the other pathogens listed.

Correct Answer: C

Rationale: The correct answer is C because Gram staining after culture on Loeffler's medium or tellurite-containing medium will show the characteristic Chinese letter arrangement of Corynebacterium diphtheriae. This arrangement consists of metachromatic granules that stain more deeply than the rest of the cell. This specific staining pattern is a key diagnostic feature of C. diphtheriae in microbiological diagnosis of diphtheria. Choice A is incorrect because simply identifying the isolate as C. diphtheriae is not sufficient for diagnosis. Choice B is incorrect as C. diphtheriae can be stained via Gram staining despite its small cell size. Choice D is incorrect as option C is indeed correct for microbiological diagnosis of diphtheria.

Correct Answer: B

Rationale: The correct answer is B: ribosome. Ribosomes are responsible for protein synthesis, not packaging. The Golgi complex (A) processes and packages proteins. The rough endoplasmic reticulum (rER) (C) is involved in protein synthesis and transport. Lysosomes (D) contain enzymes for digestion, not protein packaging. Therefore, ribosomes are the organelle directly involved in protein synthesis, making it the correct choice.