Question

Many species of bacteria regulate gene expression using a cell signaling system known as quorum sensing (qs). In this system, bacteria synthesize qs signaling molecules and release them into the surrounding environment. The effects of these molecules on gene expression depend on the density of the bacterial population. Which of the following best describes what occurs as the density of a qs bacterial population increases?

1) The concentration of qs signaling molecules increases, eventually triggering a change in gene expression in a few members of the bacterial population.
2) The concentration of qs signaling molecules decreases, eventually triggering a change in gene expression in a few members of the bacterial population.
3) The concentration of qs signaling molecules increases, eventually triggering a change in gene expression throughout the bacterial population.
4) The concentration of qs signaling molecules decreases, eventually triggering a change in gene expression throughout the bacterial population.

Answer 1

The density increase of quorum sensing bacteria leads to higher concentrations of QS signaling molecules, causing gene expression changes across the entire population. These autoinducers trigger a positive feedback loop and synchronize bacterial behavior.

Step-by-step explanation:

that as the density of a quorum sensing bacterial population increases, the concentration of QS signaling molecules also increases, eventually triggering a change in gene expression throughout the bacterial population.

Quorum sensing (QS) is a cell signaling system that bacteria use to coordinate gene expression according to the density of their population. In this communication process, bacteria produce and release QS signaling molecules into the environment. Once the concentration of these molecules reaches a threshold indicative of a sufficient population density, the molecules bind to specific bacterial receptors. This binding triggers signaling cascades that regulate gene expression and can lead to a variety of behaviors, such as virulence, biofilm formation, and bioluminescence. The autoinducers that are secreted not only signal the presence of other bacteria but also lead to an increase in the production of more signaling molecules, creating a positive feedback loop. This system allows the entire population of bacteria to synchronize their behavior in a coordinated response based on cell density.