Salmonella pathogenicity islands

Definition

Salmonella pathogenicity islands (SPIs) are distinct genetic regions in the Salmonella genome that encode various virulence factors. These regions are crucial for the bacteria's ability to cause disease and adapt to different environments.

5 Must Know Facts For Your Next Test

1. There are at least five known SPIs, with SPI-1 and SPI-2 being the most well-studied due to their roles in invasion and intracellular survival.
2. SPI-1 encodes a type III secretion system (T3SS) that helps Salmonella invade host cells by injecting effector proteins.
3. SPI-2 also encodes a T3SS, but it functions mainly within host cells to aid in the bacterium's survival and replication inside phagosomes.
4. Mutations or deletions in key genes within SPIs can significantly reduce the virulence of Salmonella strains.
5. SPIs are believed to have been acquired through horizontal gene transfer, contributing to the evolutionary success of Salmonella as a pathogen.

Review Questions

Related terms

Type III Secretion System (T3SS): A needle-like protein appendage used by some bacteria to inject effector proteins into host cells.

Horizontal Gene Transfer:

The movement of genetic material between organisms other than through vertical transmission (parent to offspring).

Phagosome:

A vesicle formed around a particle engulfed by a phagocyte via phagocytosis.