Nokea
All statements about plasmids are correct except:
- A. Many plasmids contain genes that confer resistance to one or more antibiotics
- B. Are smaller, circular, extrachromosomal DNAs
- C. Plasmids encode essential bacteria properties
- D. Plasmids are responsible for the bacterial conjugation
Correct Answer: C
Rationale: The correct answer is C because plasmids do not encode essential bacterial properties. They are non-essential, extra-chromosomal DNA molecules that can replicate independently within bacterial cells. Plasmids mainly contain genes for antibiotic resistance, genetic transfer, and other specific functions. Choice A is correct as many plasmids do carry antibiotic resistance genes. Choice B is also accurate as plasmids are indeed smaller, circular, and exist outside the bacterial chromosome. Choice D is true as plasmids can facilitate bacterial conjugation, allowing the transfer of genetic material between bacteria.
You may also like to solve these questions
Which of the following bacteria produce toxins that can lead to foodborne illnesses?
- A. Clostridium botulinum
- B. Salmonella enterica
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D. Clostridium botulinum produces botulinum toxin, Salmonella enterica produces salmonella toxin, and certain strains of Escherichia coli produce toxins like shiga toxin. These toxins can cause severe foodborne illnesses. Therefore, all of the above bacteria can produce toxins that lead to foodborne illnesses. Choices A, B, and C alone are incorrect because each of these bacteria individually can produce toxins that lead to foodborne illnesses.
The mold that produces penicillin is an example of:
- A. parasitism
- B. mutualism
- C. commensalism
- D. amensalism
Correct Answer: D
Rationale: The correct answer is D: amensalism. Penicillin mold produces a substance that inhibits the growth of bacteria, but it does not benefit nor harm the bacteria directly. This relationship is characterized by one organism (the mold) negatively affecting another (the bacteria) without any benefit or harm to itself. In parasitism (A), one organism benefits at the expense of another. In mutualism (B), both organisms benefit from the relationship. In commensalism (C), one organism benefits while the other is unaffected. Therefore, the mold producing penicillin fits the definition of amensalism.
How is viral multiplication detected in cell culture?
- A. by the presence of a specific cytopathic effect
- B. by using an immunofluorescence detection method
- C. the characteristic type of viral colonies
- D. A and B both
Correct Answer: D
Rationale: The correct answer is D because viral multiplication in cell culture can be detected by observing a specific cytopathic effect (A) caused by viral infection in cells and by using an immunofluorescence detection method (B) to visualize viral antigens within the cells. Choice C, the characteristic type of viral colonies, is incorrect as viral multiplication is not typically detected by observing viral colonies in cell culture. Option D is the correct choice as both A and B methods are commonly used to detect viral multiplication in cell culture.
A blood culture from a patient with sepsis revealed Gram-positive cocci in pairs. The bacteria were catalase-negative and alpha-hemolytic. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Enterococcus faecalis
- D. Neisseria gonorrhoeae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. This is because the bacterium is Gram-positive cocci in pairs, catalase-negative, and alpha-hemolytic, which are characteristic features of S. pneumoniae. The other choices can be ruled out based on specific characteristics: B) Staphylococcus aureus is catalase-positive, C) Enterococcus faecalis is gamma-hemolytic, and D) Neisseria gonorrhoeae is a Gram-negative diplococcus. Therefore, based on the given information, S. pneumoniae is the most likely causative agent of the sepsis.
All are correct except:
- A. Spotted fevers can be caused by Rickettsia mooseri and Rickettsia provazekii
- B. The Q-fever is transmitted only after ticks bite
- C. The Mediterranean fever is present with maculopapular rash
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B because Q-fever is not transmitted only after ticks bite; it can also be transmitted through inhalation of contaminated aerosols. Rickettsia mooseri and Rickettsia provazekii can cause spotted fevers, making choice A correct. Mediterranean fever is associated with a recurrent pattern of fever, not maculopapular rash, making choice C incorrect. "None of the above" is not correct in this case as choice B is incorrect.