Multiple Choice
Which of these is NOT true regarding bacterial plasmids?
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7. Prokaryotic Cell Structures & Functions
Introduction to Bacterial Plasmids
2:47 minutesProblem 1
Textbook Question
The removal of plasmids reduces virulence in which of the following organisms?
a. C. tetani
b. E. coli
c. S. enterica
d. S. mutans
e. C. botulinum
Verified step by step guidance1
Step 1: Understand the concept of plasmids and their role in bacterial virulence. Plasmids are small, circular DNA molecules separate from chromosomal DNA that can carry genes responsible for virulence factors such as toxins, antibiotic resistance, or adhesion molecules.
Step 2: Review the characteristics of each organism listed: C. tetani, E. coli, S. enterica, S. mutans, and C. botulinum, focusing on whether their virulence factors are plasmid-encoded or chromosomally encoded.
Step 3: Identify which organism’s virulence is known to be directly linked to plasmid-encoded genes. For example, some strains of E. coli carry plasmids that encode toxins or other virulence factors.
Step 4: Compare the role of plasmids in virulence for each organism. For instance, C. tetani and C. botulinum produce toxins encoded on their chromosomes, not plasmids, while certain E. coli strains rely on plasmids for virulence.
Step 5: Conclude that the removal of plasmids reduces virulence in the organism(s) where virulence factors are plasmid-encoded, which is typically E. coli among the options given.
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Video duration:
2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Plasmids and Their Role in Bacterial Virulence
Plasmids are small, circular DNA molecules independent of the bacterial chromosome that often carry genes beneficial for survival, including virulence factors. These extrachromosomal elements can encode toxins, adhesion factors, or antibiotic resistance, directly influencing a bacterium's ability to cause disease.
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Virulence Factors Encoded by Plasmids in Specific Bacteria
Certain bacteria rely on plasmid-encoded genes for their virulence. For example, in Escherichia coli, plasmids can carry genes for toxins and adhesion molecules, while in Clostridium species, virulence is often chromosomally encoded. Understanding which organisms depend on plasmids for virulence helps identify the impact of plasmid removal.
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Impact of Plasmid Curing on Bacterial Pathogenicity
Plasmid curing refers to the loss or removal of plasmids from bacteria, which can lead to reduced virulence if the plasmid carries essential pathogenic genes. This process is used experimentally to determine the role of plasmids in disease and can affect the bacterium's ability to infect or produce toxins.
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