Timekeeping in bacteria: the cyanobacterial circadian clock

Area of Science:

• Microbiology
• Chronobiology
• Molecular Biology

Background:

• Cyanobacteria possess an endogenous 24-hour biological clock.
• This circadian clock temporally coordinates physiological processes in prokaryotes.
• The cyanobacterial clock shares fundamental properties with eukaryotic circadian clocks.

Purpose of the Study:

• To elucidate the unique components and mechanisms of the cyanobacterial circadian clock.
• To contrast the cyanobacterial clock with those found in eukaryotes (animals, plants, fungi).
• To describe the emerging model of the cyanobacterial timing mechanism.

Main Methods:

• Comparative analysis of clock components between prokaryotes and eukaryotes.
• Investigation of the molecular machinery underlying cyanobacterial timekeeping.
• Examination of signal transduction pathways involving histidine protein kinases.

Main Results:

• Cyanobacterial clock components are non-homologous to those in animals, plants, and fungi.
• The mechanism of the cyanobacterial clock is distinct from eukaryotic models.
• A multiprotein, multimeric molecular machine is proposed for the cyanobacterial timing mechanism.
• Signal transduction involves histidine protein kinase-based phosphorylation relays.

Conclusions:

• The cyanobacterial circadian clock represents a distinct evolutionary path in biological timekeeping.
• Understanding this prokaryotic clock offers novel insights into fundamental circadian mechanisms.
• The proposed molecular machine highlights the complexity and unique adaptations of cyanobacterial physiology.