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Questions and Answers
Why are the genes encoding endotoxins located within the bacterial chromosome?
Why are the genes encoding endotoxins located within the bacterial chromosome?
- To facilitate rapid horizontal gene transfer of toxin-producing capabilities to other bacteria.
- Because endotoxins are structural components of the bacterial cell wall, essential for its integrity. (correct)
- Because endotoxins are actively secreted proteins that require complex regulation.
- To allow for easier modification of the toxin structure in response to environmental changes.
Which characteristic of exotoxins is most crucial in determining their specific action on host cells?
Which characteristic of exotoxins is most crucial in determining their specific action on host cells?
- The presence of A and B subunits, where the B subunit facilitates binding to specific host cells. (correct)
- Their heat stability, allowing them to withstand high temperatures during infection.
- Their lipopolysaccharide composition, which triggers a generalized inflammatory response.
- The presence of genes encoding them on bacterial chromosomes, ensuring stable toxin production.
Superantigens stimulate an excessive immune response by directly activating what?
Superantigens stimulate an excessive immune response by directly activating what?
- B cells, leading to massive antibody production.
- Macrophages, causing the release of TNF-alpha and IL-1.
- Complement proteins, triggering systemic inflammation.
- T cells, resulting in a cytokine storm of IL-1 and IL-2. (correct)
What is the primary mechanism by which endotoxins induce fever?
What is the primary mechanism by which endotoxins induce fever?
Which of the following explains why exotoxins, unlike endotoxins, often require specific transport or binding mechanisms to enter host cells?
Which of the following explains why exotoxins, unlike endotoxins, often require specific transport or binding mechanisms to enter host cells?
How does the genetic mobility of exotoxin-encoding genes contribute to bacterial pathogenicity?
How does the genetic mobility of exotoxin-encoding genes contribute to bacterial pathogenicity?
What is the most significant implication of endotoxins activating the coagulation cascade?
What is the most significant implication of endotoxins activating the coagulation cascade?
Why are exotoxins generally more potent than endotoxins?
Why are exotoxins generally more potent than endotoxins?
Which feature primarily explains why endotoxins induce a systemic response, such as fever and shock?
Which feature primarily explains why endotoxins induce a systemic response, such as fever and shock?
How does the heat stability of endotoxins affect sterilization protocols in medical settings?
How does the heat stability of endotoxins affect sterilization protocols in medical settings?
Flashcards
Exotoxins
Exotoxins
Toxins produced inside gram-positive bacteria and released into the surrounding medium, or secreted.
Endotoxins
Endotoxins
Part of the outer cell wall of gram-negative bacteria, released when the bacteria die and the cell wall breaks apart releasing the toxin.
Location of genes encoding endotoxins
Location of genes encoding endotoxins
Located in bacterial chromosomes and are an integral part of the bacteria.
Location of genes encoding exotoxins
Location of genes encoding exotoxins
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Exotoxin B subunit function
Exotoxin B subunit function
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Exotoxin A subunit function
Exotoxin A subunit function
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Mechanism of endotoxins
Mechanism of endotoxins
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Superantigens
Superantigens
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Exotoxin characteristics
Exotoxin characteristics
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Endotoxin characteristics
Endotoxin characteristics
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Study Notes
- Two main types of bacterial toxins exist: exotoxins and endotoxins.
Exotoxins
- Exotoxins are produced inside Gram-positive bacteria.
- Exotoxins are secreted or released upon lysis into the surrounding medium.
- Exotoxins are polypeptides produced by certain species of both Gram-positive and Gram-negative bacteria.
- Exotoxins are highly toxic.
- Exotoxins are sensitive to heat.
- Examples of diseases caused by exotoxins include tetanus, botulism, and diphtheria.
- Genes encoding exotoxins are present in bacterial plasmids and bacteriophage DNA.
- Most exotoxins contain A and B subunits.
- The B subunit aids in binding to the host cell.
- The A subunit is the active component causing toxic effects.
Endotoxins
- Endotoxins form part of the outer layer of the cell wall in certain Gram-negative bacteria.
- Endotoxins are released into the medium when bacteria die and the cell wall breaks apart.
- Endotoxins are lipopolysaccharides (LPS) that are part of the cell wall of Gram-negative bacteria.
- Endotoxins are relatively less toxic.
- Endotoxins are highly stable, even at high temperatures.
- Examples of diseases caused by endotoxins are meningococcemia and sepsis.
- Genes encoding endotoxins are located on bacterial chromosomes, making them an integral part of the bacteria.
- Lipopolysaccharide (LPS) consists of a phospholipid called lipid A, a core polysaccharide, and an outer polysaccharide.
- Lipid A is responsible for the toxic effects of endotoxins.
- Endotoxins activate macrophages, leading to the production of IL-1, TNF, and nitric oxide, resulting in fever and hypotension.
- Endotoxins activate complement, causing hypotension and edema.
- Endotoxins activate tissue factor, which leads to disseminated intravascular coagulation, causing blood clots.
Superantigens
- Superantigens non-specifically activate T cells.
- Superantigens result in the production of large amounts of IL-1 and IL-2.
- This process leads to the death of T cells, resulting in the loss of specific T cell clones.
- Examples of superantigens include toxic shock syndrome toxin (produced by Staphylococcus aureus) and erythrogenic toxin (produced by Streptococcus pyogenes).
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