Which viral replication strategy involves reverse transcription of RNA to DNA?

The correct answer is A: Retroviral replication. Retroviruses like HIV use reverse transcriptase to synthesize DNA from their RNA genome for integration into host DNA.

Which of the following bacterial cell wall components is responsible for the Gram-positive purple coloration in Gram staining?

The correct answer is A: Thick peptidoglycan layer with teichoic acids. Gram-positive bacteria have a thick peptidoglycan layer (20-80 nm) with teichoic acids that retains the crystal violet-iodine complex, resulting in purple coloration.

Which viral enzyme is responsible for integrating retroviral DNA into the host genome?

The correct answer is A: Integrase. Integrase catalyzes the insertion of viral DNA into the host chromosome, establishing persistent infection in retroviruses like HIV.

A patient presents with atypical pneumonia. Which bacterial pathogen should be considered if Gram staining shows no organism but PCR is positive?

The correct answer is A: Mycoplasma pneumoniae. Mycoplasma lacks a cell wall and does not stain with Gram staining but is detectable by PCR, causing atypical pneumonia.

A nosocomial infection outbreak is linked to environmental contamination by Acinetobacter baumannii. Which characteristic makes this organism particularly difficult to eradicate?

The correct answer is A: Formation of biofilms and environmental persistence. Acinetobacter baumannii forms robust biofilms on environmental surfaces and medical devices, surviving desiccation and disinfection, complicating infection control.

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Microbiology
Bacteria & Viruses

Bacteria, viruses, immunology, genetics

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All Bacteria & Viruses 100

Q.31 Easy Bacteria & Viruses

Which of the following bacteria is gram-positive and forms spores?

A Bacillus subtilis

B Escherichia coli

C Vibrio cholerae

D Pseudomonas aeruginosa

Correct Answer: A. Bacillus subtilis

EXPLANATION

Bacillus subtilis is a gram-positive, rod-shaped bacterium capable of forming endospores. E. coli is gram-negative, V. cholerae is gram-negative curved rod, and P. aeruginosa is gram-negative.

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