Quorum sensing is:
a. The ability to respond to changes in population density
b. A characteristic allowing secretion of a matrix
c. Dependent on direct contact among cells
d. Associated with colonies in broth culture

Verified step by step guidance

1. Understand that quorum sensing is a communication mechanism used by bacteria to coordinate certain behaviors based on their population density.
2. Recall that quorum sensing involves the production, release, and detection of signaling molecules called autoinducers, which accumulate as the bacterial population grows.
3. Recognize that when the concentration of these signaling molecules reaches a threshold, it triggers a coordinated response in the bacterial community, such as gene expression changes.
4. Evaluate each option in the question: (a) relates to responding to population density, (b) secretion of a matrix, (c) direct contact among cells, and (d) association with colonies in broth culture.
5. Conclude that the best description of quorum sensing is the ability to respond to changes in population density, which matches option (a).

Key Concepts

Quorum Sensing

Quorum sensing is a communication mechanism used by bacteria to detect and respond to changes in their population density through the production and detection of signaling molecules called autoinducers. This process enables coordinated gene expression across the bacterial community.

Autoinducers and Signal Molecules

Autoinducers are chemical signals secreted by bacteria that accumulate in the environment as the population grows. When a threshold concentration is reached, these molecules trigger changes in gene expression, allowing bacteria to synchronize behaviors such as biofilm formation or virulence.

Population Density-Dependent Regulation

Quorum sensing relies on the density of bacterial cells; it is not dependent on direct physical contact but on the concentration of signaling molecules in the environment. This allows bacteria to coordinate activities only when a sufficient number of cells are present.