Not many bacterial species in nature form spores. Which of the following genera have this ability?

Correct Answer: C

Rationale: The correct answer is C: Bacillus, Clostridium. Both Bacillus and Clostridium are known to form spores. Bacillus species produce endospores, which are resistant structures for survival in harsh conditions, while Clostridium species also form spores for protection and dispersal. The other choices are incorrect because Borrelia and Treponema are spirochetes and do not form spores, Bacteroides and Fusobacterium are anaerobic bacteria that do not produce spores, and Bordetella and Brucella are non-spore forming bacteria as well.

Correct Answer: A

Rationale: Step-by-step rationale for why the correct answer is A (Cholera): 1. Gram-negative curved mobile monotrichous bacilli: Vibrio cholerae, the causative agent of cholera, fits this description. 2. Do not produce spores or capsules: Vibrio cholerae does not produce spores or capsules. 3. Require alkaline reaction (pH 8.5-9.5): Vibrio cholerae thrives in alkaline environments. 4. Enteric infection: Cholera is a classic example of an enteric infection transmitted through contaminated food or water. Summary of why other choices are incorrect: B: Shigellosis is caused by Shigella species, which are gram-negative, but they are not curved bacilli and do not require an alkaline pH. C: Typhoid fever is caused by Salmonella Typhi, which are gram-negative but are not curved bacilli and do not require an alkaline pH.

Correct Answer: A

Rationale: The correct answer is A: Lowestein-Jensen. This is because Lowestein-Jensen medium is specifically designed to cultivate Mycobacterium tuberculosis, providing necessary nutrients and conditions for its growth. Loefller's medium is not optimal for cultivating M. tuberculosis. Choice C (All of the above) is incorrect as not all the options listed are suitable for cultivating M. tuberculosis. Choice D (None of the above) is also incorrect as Lowestein-Jensen is indeed the recommended growth medium for this bacterium.

Correct Answer: A

Rationale: The correct answer is A because the cloudy surface indicates that the bacteria are growing where oxygen is present (aerobes), causing turbidity. The clear bottom suggests that the bacteria are not growing in the absence of oxygen. Choices B, C, and D are incorrect because the observed phenomena do not necessarily indicate the need for an anaerobic chamber, enzyme deficiencies, or the microorganism being non-aerotolerant.

Correct Answer: A

Rationale: The correct answer is A: Tuberculine. The Mantoux test involves injecting tuberculin, a protein derivative of Mycobacterium tuberculosis, under the skin. This test helps determine if a person has been exposed to the bacteria that cause TB. Administering tuberculin is crucial for the Mantoux test as it triggers a delayed-type hypersensitivity reaction in individuals previously exposed to TB. Choice B (BCG vaccine) is incorrect because BCG does not interfere with the Mantoux test results. Choice C (DPT vaccine) is incorrect as it is used for immunization against diphtheria, pertussis, and tetanus, not for diagnosing TB. Choice D (Tularin test) is incorrect as it is not a recognized immunobiological agent for TB diagnosis.

Correct Answer: B

Rationale: The correct answer is B: Family Reoviridae. Reassortment of gene segments occurs in segmented viruses like Reoviruses. In Reoviridae, each segment encodes a specific protein, allowing for reassortment to generate new strains. Togaviridae (A) is a non-segmented virus, not capable of reassortment. Picornaviridae (C) and Paramyxoviruses (D) are also non-segmented viruses, limiting their ability for reassortment. Therefore, the correct choice is B due to the segmented nature of Reoviruses allowing for genetic reassortment.

Correct Answer: A

Rationale: The correct answer is A because it accurately describes the major morphological forms of bacteria. Cocci are spherical, rod-shaped bacteria are called bacilli, and curved bacteria are spirilla. Staphylococci, streptococci, and diplococci are specific types of cocci, not major morphological forms. Basicili and spiralis are not common morphological forms of bacteria. Option D is incorrect as the other choices do represent major morphological forms of bacteria.

Correct Answer: D

Rationale: The correct answer is D: Agar media. Influenza viruses cannot be isolated in agar media because they require specific conditions present in laboratory animals, embryonated eggs, or cell cultures for successful isolation and propagation. Agar media lack the necessary components and environment needed for influenza virus replication. In laboratory animals, such as mice, the viruses can replicate and cause infection. Embryonated eggs provide a suitable environment for influenza virus growth and isolation due to the presence of necessary nutrients and factors. Cell cultures offer controlled conditions for virus propagation and study, making them a valuable tool in influenza virus research.

Correct Answer: A

Rationale: The correct answer is A: tRNA. Anticodons are sequences of nucleotides found on tRNA molecules that complement the codons on mRNA during translation. tRNA molecules carry specific amino acids to the ribosome based on the codon-anticodon pairing. Option B, rRNA, forms the structure of the ribosome and is not directly involved in anticodon recognition. Option C, mRNA, contains codons but not anticodons. Option D, ribosomes, are the site of protein synthesis but do not contain the anticodons themselves.