Daily rhythmicity in coastal microbial mats

Area of Science:

• Microbiology
• Molecular Biology
• Ecology

Background:

• Cyanobacteria are key primary producers in coastal microbial mats, supplying essential nutrients.
• Circadian clocks regulate cyanobacterial metabolism and growth, but their function in natural communities is poorly understood.

Purpose of the Study:

• To investigate daily gene expression rhythms in a coastal microbial mat community.
• To identify genes with diel expression patterns and understand the role of circadian clocks in microbial mats.

Main Methods:

• Collected microbial mat samples over a 24-hour period.
• Analyzed meta-transcriptome data using periodic function fitting to identify rhythmic gene expression.
• Utilized MG-RAST annotation and mRNA recruitment analysis to confirm gene presence and function.

Main Results:

• Approximately 7% of 24,035 conserved gene transcript clusters showed significant rhythmic expression.
• Rhythmic genes were found in phototrophic micro-eukaryotes, cyanobacteria, proteobacteria, and bacteroidetes.
• Homologs of cyanobacterial circadian clock genes were identified in other bacterial members, indicating widespread molecular clocks.

Conclusions:

• Microbial mats exhibit complex daily rhythms driven by multiple bacterial groups, not just cyanobacteria.
• Various microbial mat members possess their own molecular clocks, influenced by environmental cues (Zeitgebers) and inter-species interactions.
• Microbial mats function as integrated systems where different microbial sub-systems coordinate their timing for optimal community function.