74. Which sporulation bacteria possess cell-cell communication mechanism that allows bacteria to coordinate physiological processes in response to cell density?
(1) Actinomycetes

(2) Bacillus subtilis
(3) Cyanobacteria
(4) Archeabacteria

Sporulating Bacteria and Cell-Cell Communication: Role of Quorum Sensing in Bacillus subtilis

Introduction

Cell-cell communication in bacteria, particularly during sporulation, is crucial for coordinating complex physiological processes such as biofilm formation, competence, and spore development. This coordination often depends on a mechanism called quorum sensing (QS), where bacteria produce and detect signaling molecules called autoinducers to regulate gene expression in a population density–dependent manner.

Which Sporulating Bacteria Use Quorum Sensing?

Among the options:

1. Actinomycetes — Known for filamentous growth and producing spores, but quorum sensing is less characteristic or well-defined than in Bacillus.

2. Bacillus subtilis — A Gram-positive, endospore-forming bacterium, widely studied for its quorum sensing systems that regulate social behaviors, sporulation, biofilm formation, and competence.

3. Cyanobacteria — Photosynthetic bacteria that do form spores (akinetes), but classical quorum sensing systems similar to Bacillus are less typical.

4. Archaebacteria — Archaeal species, not commonly characterized by quorum sensing mechanisms for sporulation.

Evidence for Bacillus subtilis Quorum Sensing

Research (see citations , , and ) demonstrates that Bacillus subtilis utilizes quorum sensing through peptide signals and receptor systems (e.g., ComQXP and Rap-Phr) to regulate gene expression linked to sporulation and other cooperative behaviors. QS allows B. subtilis to sense cell density and coordinate the initiation of sporulation, balancing growth and survival strategies.​

Studies show:

• Secretion and detection of peptide autoinducers that accumulate with cell density.

• Activation of transcription factors in response to QS signals.

• Regulation of sporulation initiation through QS pathways.

• QS mutants display altered sporulation and biofilm phenotypes.

Thus, QS provides a population-level regulatory mechanism that aligns sporulation timing among cells, functioning as a bet hedging strategy in variable environments.

Summary

The sporulating bacterium that possesses a well-characterized cell-cell communication mechanism for coordinating physiological processes in response to cell density is:

(2) Bacillus subtilis