The bacterium ends up perched on a “throne”, a stalk protuberance of the gut cell arising from the gut surface. Molecules of what common protein are polymerized into a string of yellow beads to form the fibers that push up the membrane under the bacterium and form this “throne”
The correct answer and explanation is:
Correct answer: Actin
Explanation:
The “throne” described is a stalk-like protuberance on the gut cell surface formed under a bacterium. This structure is created by the polymerization of actin molecules into long filamentous fibers. Actin is a very common and essential protein found in all eukaryotic cells, where it plays a crucial role in maintaining cell shape, enabling cell movement, and facilitating intracellular transport.
How actin forms the “throne”:
When certain bacteria attach to gut epithelial cells, they manipulate the host cell’s cytoskeleton to form specialized structures that support their adhesion. The bacterium signals the host cell to polymerize actin monomers (G-actin) into filamentous actin (F-actin), creating a dense bundle or pedestal beneath the site of bacterial attachment. This pedestal looks like a string of yellow beads under microscopic imaging because actin filaments appear as bead-like subunits when labeled.
Significance of actin polymerization:
- Structural support: The polymerized actin fibers push up the plasma membrane, forming the elevated “throne” or pedestal on which the bacterium sits. This provides a stable platform for the bacterium to stay attached without being easily removed by gut movements or mucus flow.
- Pathogenic strategy: Many pathogenic bacteria, such as enteropathogenic Escherichia coli (EPEC), use this mechanism to establish infection. By hijacking the host’s actin cytoskeleton, they can anchor tightly and resist mechanical clearance, increasing their ability to cause disease.
- Host-pathogen interaction: This process is an example of how pathogens manipulate host cell machinery to their advantage. It also triggers changes in the host cell signaling and cytoskeletal rearrangements, which may contribute to disease symptoms.
In summary, the common protein actin is polymerized into filaments that form the “throne” structure, enabling the bacterium to perch securely on the gut cell surface. This actin-based pedestal is a key aspect of how some bacteria adhere to and manipulate host cells during infection.