21 Questions
Explain the role of effector proteins in the pathogenesis of Salmonella infection.
Effector proteins are enzymes released by Salmonella that harm the host by disrupting normal cellular functions. For example, SopB (SPI-5) causes osmotic imbalance in host cells, leading to water and nutrient loss.
What are some examples of cellular structures that assist Salmonella in persistence and adhesion?
Capsules, pilus, and fimbrae are cellular structures that assist Salmonella in persistence and adhesion to host cells.
Distinguish between Typhoidal and Non-Typhoidal Salmonella.
Healthy Salmonella Enterica are part of the microbiota in humans and play a commensalist role, while Typhoidal Salmonella causes serious and possibly fatal illness by invading the cells of the host lining the epithelium and leading to bacterial proliferation in the bloodstream and organs.
Describe the effector mechanisms of Salmonella that lead to Typhoid fever.
Salmonella evades the immune system by escaping the phagocyte (SPI-2) and inhibiting the fusion of the lysosome to the macrophage. It also forms Salmonella Containing Vacuoles (SCVs) which can become Salmonella Induced Filaments (SIFs) to penetrate tissue and enter the bloodstream for further replication and proliferation.
What are pathogenicity islands and what is their significance in the context of microbial pathogenesis?
Pathogenicity islands are genomic islands with multiple virulence factors. They are genetic loci with one or more coding genes and different GC content than the rest of the genome, indicating horizontal gene transfer. They play a significant role in the acquisition and expression of virulence traits in pathogenic microbes.
How does Salmonella evade destruction through the immune system?
Salmonella evades destruction through the immune system by escaping the phagocyte (SPI-2) and inhibiting the fusion of the lysosome to the macrophage. It also forms internal reservoirs like Salmonella Containing Vacuoles (SCVs) and Salmonella Induced Filaments (SIFs) to penetrate tissue, enter the bloodstream, and allow for further replication and proliferation.
Explain the impact of Typhoidal Salmonella on the host and the mechanisms by which it causes illness.
Typhoidal Salmonella causes serious and possibly fatal illness by invading the cells of the host lining the epithelium, leading to bacterial proliferation in the bloodstream and organs, causing sepsis. It also activates immune cells and evades the immune system through various mechanisms, leading to the progression of the illness.
What are some examples of virulence factors involved in Salmonella pathogenesis?
Examples of virulence factors involved in Salmonella pathogenesis include effector proteins like SopB (SPI-5), secretion systems, and cellular structures such as capsules, pilus, and fimbrae that assist with persistence and adhesion.
What are the distinct roles of Salmonella Pathogenicity Islands (SPI) 1, 2, and 5 in the invasion and survival of Salmonella within host cells?
SPI-1 is associated with the invasion of host cells, SPI-2 is responsible for survival within host cells, and SPI-5's function is debated but plays a role in both intra- and extracellular survival of Salmonella.
Which master regulator is associated with the regulation of SPI-1?
HilA is the master regulator associated with the regulation of SPI-1.
What is the role of SPI-2 and which master regulator regulates it?
SPI-2 is responsible for survival within host cells, and it is regulated by the master regulator SsrAB.
How does heat stress impact the expression of SsrB and SPI-2 genes in Salmonella?
Heat stress increases the expression of SsrB and SPI-2 genes, potentially leading to more virulent Salmonella in improperly cooked food.
What are the distinct roles of different types of secretion systems (Type II, III, IV) in bacterial virulence?
Different types of secretion systems have distinct mechanisms of compound secretion and play roles in bacterial virulence.
What is the function of bacterial capsules and pili in relation to bacterial virulence?
Bacterial capsules aid in persistence and evasion of immune detection, while pili are involved in adhesion to host cells.
What are the differences between endotoxins and exotoxins in terms of their release and effects?
Endotoxins are released when bacterial cells are destroyed, causing inflammatory responses, while exotoxins are secreted by microbes and have toxic effects on host cells.
Provide an example of an exotoxin and its subunit composition.
Anthrax toxin, produced by Bacillus anthracis, is an example of an exotoxin with two A subunits and a B subunit.
What are the immune evasion strategies employed by prokaryotes and protozoans?
Prokaryotic immune evasion strategies include antigenic masking and variation, while protozoans use immunosuppression to evade the eukaryotic immune system.
How does viral latency contribute to the pathogenesis of infection, and provide an example of a virus that establishes latency in nerve cells.
Viral latency plays a role in the pathogenesis of infection, with herpes simplex virus being an example of a virus that establishes latency in nerve cells.
Which type of Salmonella Pathogenicity Island (SPI) is associated with the invasion of host cells?
SPI-1
What is the impact of heat stress on Salmonella virulence?
Increases expression of SsrB and SPI-2 genes
What is the role of bacterial capsules in relation to immune detection and persistence?
Aid in persistence and evasion of immune detection
Study Notes
Regulation of Gene Expression and Bacterial Virulence
- Salmonella Pathogenicity Islands (SPI) 1, 2, and 5 play distinct roles in the invasion and survival of Salmonella within host cells.
- SPI-1 is associated with the invasion of host cells and is regulated by the master regulator HilA.
- SPI-2 is responsible for survival within host cells and is regulated by the master regulator SsrAB.
- SPI-5's function is debated, but it plays a role in both intra- and extracellular survival of Salmonella.
- Heat stress increases the expression of SsrB and SPI-2 genes, potentially leading to more virulent Salmonella in improperly cooked food.
- Different types of secretion systems (Type II, III, IV) have distinct mechanisms of compound secretion and play roles in bacterial virulence.
- Bacterial capsules aid in persistence and evasion of immune detection, while pili are involved in adhesion to host cells.
- Endotoxins are released when bacterial cells are destroyed, causing inflammatory responses, while exotoxins are secreted by microbes and have toxic effects on host cells.
- Anthrax toxin, produced by Bacillus anthracis, is an example of an exotoxin with two A subunits and a B subunit.
- Prokaryotic immune evasion strategies include antigenic masking and variation, while protozoans use immunosuppression to evade the eukaryotic immune system.
- Viral latency plays a role in the pathogenesis of infection, with herpes simplex virus being an example of a virus that establishes latency in nerve cells.
Regulation of Gene Expression and Bacterial Virulence
- Salmonella Pathogenicity Islands (SPI) 1, 2, and 5 play distinct roles in the invasion and survival of Salmonella within host cells.
- SPI-1 is associated with the invasion of host cells and is regulated by the master regulator HilA.
- SPI-2 is responsible for survival within host cells and is regulated by the master regulator SsrAB.
- SPI-5's function is debated, but it plays a role in both intra- and extracellular survival of Salmonella.
- Heat stress increases the expression of SsrB and SPI-2 genes, potentially leading to more virulent Salmonella in improperly cooked food.
- Different types of secretion systems (Type II, III, IV) have distinct mechanisms of compound secretion and play roles in bacterial virulence.
- Bacterial capsules aid in persistence and evasion of immune detection, while pili are involved in adhesion to host cells.
- Endotoxins are released when bacterial cells are destroyed, causing inflammatory responses, while exotoxins are secreted by microbes and have toxic effects on host cells.
- Anthrax toxin, produced by Bacillus anthracis, is an example of an exotoxin with two A subunits and a B subunit.
- Prokaryotic immune evasion strategies include antigenic masking and variation, while protozoans use immunosuppression to evade the eukaryotic immune system.
- Viral latency plays a role in the pathogenesis of infection, with herpes simplex virus being an example of a virus that establishes latency in nerve cells.
Test your knowledge of gene expression regulation and bacterial virulence with this quiz! Explore topics such as Salmonella Pathogenicity Islands, bacterial secretion systems, capsules and pili, endotoxins and exotoxins, immune evasion strategies, and viral latency.
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