Which bacteria are capable of producing spores that can survive extreme environmental conditions?

Correct Answer: C

Rationale: The correct answer is C (Both A and B) because both Clostridium botulinum and Bacillus anthracis are capable of producing spores. Spores are highly resistant structures that allow bacteria to survive harsh environmental conditions. Clostridium botulinum and Bacillus anthracis produce spores as a survival mechanism when conditions become unfavorable. Choice A (Clostridium botulinum) is incorrect because it only represents one of the bacteria capable of producing spores. Choice B (Bacillus anthracis) is also incorrect as it alone does not encompass all bacteria capable of producing spores. Choice D (None of the above) is incorrect as both bacteria mentioned can produce spores.

Correct Answer: A

Rationale: The correct answer is A. Rubella virus has icosahedral type of symmetry due to its spherical shape with 20 faces. This symmetry allows for efficient packaging of genetic material and structural stability. Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA. Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane. Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface that aid in host cell recognition and entry.

Correct Answer: A

Rationale: The correct answer is A: 20 minutes. Escherichia coli has a short generation time, typically around 20 minutes. This means that under ideal conditions, one bacterium can divide and produce two daughter cells every 20 minutes. This rapid growth rate is a characteristic of E. coli and is important in various fields such as microbiology and biotechnology. Choice B (60 minutes) and Choice C (20 hours) are incorrect as they do not align with the typical generation time of E. coli. Choice D (24 hours) is also incorrect as it is too long for the generation time of E. coli.

Correct Answer: B

Rationale: The correct answer is B: Staphylococcus epidermidis. This bacterium is a normal skin flora commonly found on human skin. It is part of the skin microbiota and helps protect against pathogenic organisms. Streptococcus pyogenes (A), Pseudomonas aeruginosa (C), and Acinetobacter baumannii (D) are not normal skin flora. Streptococcus pyogenes is a pathogenic bacterium causing various infections, Pseudomonas aeruginosa is an opportunistic pathogen commonly found in water and soil, and Acinetobacter baumannii is associated with healthcare-associated infections.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a protozoan parasite that causes foul-smelling diarrhea with trophozoites having two nuclei and flagella in stool microscopy. The presence of flagella and two nuclei is characteristic of Giardia lamblia. Entamoeba histolytica (Choice B) causes amoebic dysentery with trophozoites containing ingested RBCs. Trichomonas vaginalis (Choice C) is a sexually transmitted protozoan causing vaginitis with a distinctive pear-shaped trophozoite. Balantidium coli (Choice D) is a ciliated protozoan causing diarrhea with trophozoites containing a single nucleus.

Correct Answer: A

Rationale: The correct answer is A: Streptomycin. Streptomycin is an aminoglycoside antibiotic used to treat tuberculosis that can cause hearing loss as a side effect. It is known to damage the cochlear and vestibular organs in the inner ear. The other choices, B: Isoniazid, C: Rifampicin, and D: Ethionamide, are not associated with causing hearing deterioration as a side effect. Isoniazid can rarely cause peripheral neuropathy, Rifampicin can lead to hepatotoxicity, and Ethionamide may cause gastrointestinal disturbances, but none of these drugs are known to specifically cause hearing loss.

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: A

Rationale: The correct answer is A: Entamoeba histolytica. This is because it is a protozoan parasite known to cause amoebic dysentery, presenting with chronic diarrhea and cysts with four nuclei in the stool sample. Giardia lamblia (B) causes giardiasis with trophozoites and cysts with two nuclei. Balantidium coli (C) is a ciliated parasite causing dysentery with large trophozoites. Trichomonas hominis (D) is a non-pathogenic flagellate often found in the human intestine. Thus, based on the specific characteristics of the cysts and clinical presentation, Entamoeba histolytica is the most likely causative agent.