A bacterial signaling system that regulates population density-dependent gene expression using secreted chemical signals is known as:
A bacterial signaling system that regulates population density-dependent gene expression using secreted chemical signals is known as:
Select an option to attempt
Correct Answer: Option B
Explanation
Quorum sensing in bacteria:Quorum sensing (QS) is a cell density-dependent gene regulation mechanism:1. Bacteria continuously secrete small diffusible signalling molecules called autoinducers (AIs):• Gram-negative: N-acyl homoserine lactones (AHLs) — e.g., LasI/LasR in Pseudomonas aeruginosa• Gram-positive: short oligopeptides (AIPs)• Universal: AI-2 (furanosyl borate diester)2. As population density increases, autoinducer concentration accumulates.3. When [autoinducer] exceeds a threshold, it binds its receptor → transcription factor activated → gene expression changes.Genes regulated by QS include: biofilm formation, virulence factors, bioluminescence (Vibrio fischeri), antibiotic synthesis.Key concept: QS allows bacteria to 'sense' population density and coordinate collective behaviour (act as a multicellular community).Answer: Quorum sensing uses secreted autoinducers that accumulate with population density to regulate gene expression at a threshold.