Precise circadian clocks in prokaryotic cyanobacteria

Area of Science:

• Microbiology
• Molecular Biology
• Chronobiology

Background:

• Prokaryotic cyanobacteria exhibit robust circadian rhythms.
• These biological clocks are independent of the cell division cycle.
• The clock regulates global gene expression and cell division timing.

Purpose of the Study:

• To describe the cyanobacterial biological clock mechanism.
• To identify key clock genes and proteins.
• To propose a model for the core clockwork and its adaptive value.

Main Methods:

• Protein identification in input pathways.
• Mutational screening to identify clock genes.
• Analysis of protein structure, phosphorylation, and regulation.
• Mixed-strain competition experiments.

Main Results:

• Three cyanobacterial clock genes identified as a gene cluster.
• Detailed description of clock protein structure, phosphorylation, and regulation.
• A new model proposing rhythmic chromosome status underlies gene expression rhythms.
• Demonstration of adaptive value in mixed-strain competition.

Conclusions:

• Cyanobacteria possess a sophisticated, cell-cycle-independent circadian clock.
• Rhythmic chromosome status is a key component of the cyanobacterial core clockwork.
• The circadian timing mechanism confers a competitive advantage.