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 (300 words):
The bacterium described is manipulating the host’s cellular machinery to form a “throne” — a protrusion that elevates it above the surface of the gut cell. This structure is created using actin, a common and crucial protein in eukaryotic cells. Actin is highly conserved and plays a vital role in maintaining cell shape, enabling movement, and facilitating intracellular transport.
In the context of bacterial infection, certain pathogenic bacteria like Salmonella and Enteropathogenic E. coli (EPEC) are known to hijack the host’s actin cytoskeleton to benefit their own survival and proliferation. These bacteria inject specialized proteins into the host cell through a type III secretion system. These injected proteins trigger the rapid polymerization of actin beneath the site of attachment, pushing the cell membrane upwards and forming pedestal-like structures.
This actin polymerization is visually described as a string of yellow beads, which likely refers to the polymerized actin filaments (F-actin). Individual actin monomers (G-actin) come together in a helical structure to form these long filaments. When enough filaments accumulate and organize beneath the site where the bacterium attaches, they exert an upward force on the membrane, resulting in a visible bump or stalk — the so-called “throne”.
This mechanism serves the bacterium in several ways:
- It allows the microbe to remain attached firmly to the host cell despite gut fluid movement.
- It helps the pathogen avoid detection by immune cells.
- It provides a localized niche for accessing nutrients or injecting more virulence factors.
In summary, the “throne” structure beneath the bacterium is formed by the polymerization of actin, which is repurposed by the bacterium from its usual cellular roles to construct a supportive pedestal beneath itself.