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A wound smear revealed Gram-negative rods producing blue-green pigment. The bacteria had a fruity odor. What is the causative agent?
- A. Pseudomonas aeruginosa
- B. Escherichia coli
- C. Klebsiella pneumoniae
- D. Proteus mirabilis
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known to produce a blue-green pigment called pyocyanin, which is characteristic of the organism. Additionally, it has a distinct fruity odor due to the production of certain volatile compounds. Escherichia coli (B) does not produce blue-green pigment or have a fruity odor. Klebsiella pneumoniae (C) and Proteus mirabilis (D) also do not exhibit these specific characteristics associated with Pseudomonas aeruginosa.
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The bacterial genome is typically composed of:
- A. double-stranded RNA
- B. linear DNA
- C. circular double-stranded DNA
- D. single-stranded DNA
Correct Answer: C
Rationale: The correct answer is C: circular double-stranded DNA. Bacterial genomes are typically composed of circular double-stranded DNA due to its stability and efficient replication. Circular DNA allows for continuous replication without the need for telomeres present in linear DNA (choice B). Bacteria do not typically have double-stranded RNA genomes (choice A) as RNA is more commonly found in viruses. Single-stranded DNA (choice D) is not typically the main genetic material in bacteria, as it is less stable and less efficient for information storage compared to double-stranded DNA.
An enzyme process of producing two identical copies of DNA from one original DNA molecule is called:
- A. Translation
- B. Transcription
- C. Replication
- D. Cell division
Correct Answer: C
Rationale: The correct answer is C: Replication. In DNA replication, the original DNA molecule is unwound and each strand serves as a template to synthesize a new complementary strand. This results in two identical copies of the original DNA molecule. Translation (A) is the process of synthesizing proteins from mRNA. Transcription (B) is the process of synthesizing mRNA from DNA. Cell division (D) is the process of a cell dividing into two daughter cells, not specifically producing identical DNA copies. Therefore, replication is the correct answer as it specifically refers to the process of copying DNA to produce two identical copies.
A bacterial colony is:
- A. Visible formation, formed by clustering of cells, belonging to different bacterial species
- B. Formed only on a liquid nutrient medium
- C. Both are incorrect
- D. None of the above
Correct Answer: A
Rationale: Step 1: A bacterial colony is a visible formation: Correct as colonies are visible to the naked eye.
Step 2: Formed by clustering of cells: Correct as colonies are made up of numerous bacterial cells.
Step 3: Belonging to different bacterial species: Correct as colonies can consist of one or multiple species.
Summary:
Choice A is correct as it accurately describes a bacterial colony. Choice B is incorrect as colonies can also form on solid nutrient mediums. Choice C is incorrect as choice A is correct. Choice D is incorrect as there is a correct option provided.
Disinfection is:
- A. method for destruction of spore forms of microorganisms
- B. method for destruction of vegetative and spore forms of microorganisms
- C. method to destroy the vegetative forms of microorganism, but their spores may survive
- D. method for determination of the effect of physical agents on the microorganism
Correct Answer: C
Rationale: Disinfection is the process of destroying the vegetative forms of microorganisms, but their spores may survive. This is why choice C is correct. The other choices are incorrect because:
A: Disinfection does not necessarily target spore forms exclusively.
B: While disinfection targets vegetative forms, it does not always eliminate spore forms.
D: Disinfection is not primarily used for determining the effect of physical agents on microorganisms.
Which of the following microorganisms are always in a parasitic form of interaction with the individual?
- A. viruses
- B. non-pathogenic bacteria
- C. facultative pathogenic bacteria
- D. all listed above
Correct Answer: A
Rationale: The correct answer is A: viruses. Viruses are always in a parasitic form of interaction with the individual because they cannot survive or reproduce outside of a host cell. They rely on host cells to replicate and cause harm. Non-pathogenic bacteria (choice B) do not always cause harm and can coexist with the individual. Facultative pathogenic bacteria (choice C) can switch between being beneficial and harmful. Therefore, the correct answer is A as viruses always rely on a host for survival and reproduction.