Circadian clock-controlled gene expression in co-cultured, mat-forming cyanobacteria

Area of Science:

• Microbial Ecology
• Cyanobacteria
• Circadian Biology

Background:

• Natural microbial mats are complex communities shaped by competition and cooperation under fluctuating conditions.
• Laboratory studies often simplify microbial communities, using homogeneous monocultures in liquid media, which doesn't reflect natural complexity.
• Understanding the circadian regulation in key mat-forming species is crucial for ecological insights.

Purpose of the Study:

• To investigate the expression of circadian clock genes (kaiA, kaiB, kaiC) and their controlled genes in Lyngbya aestuarii and Coleofasciculus chthonoplastes.
• To determine how environmental factors such as co-culturing and substrate (liquid vs. solid) influence circadian gene expression.
• To compare the circadian patterns between these two mat-forming cyanobacteria species.

Main Methods:

• Culturing of Lyngbya aestuarii and Coleofasciculus chthonoplastes in monocultures and co-cultures on liquid media or solid substrates (glass beads).
• Exposure to a light-dark cycle followed by transfer to continuous light conditions.
• Quantitative PCR (qPCR) using TaqMan probes to measure the expression levels of kaiABC and clock-controlled genes (psbA, nifH, ftsZ, prx).

Main Results:

• Circadian clock gene (kaiABC) expression was significantly influenced by co-culturing and the growth substrate.
• A free-running circadian expression cycle was observed in Lyngbya aestuarii but not in Coleofasciculus chthonoplastes under continuous light.
• In L. aestuarii, psbA and nifH expression peaked at different times, independent of the light regime, with peak timing shifting under continuous illumination.

Conclusions:

• Lyngbya aestuarii and Coleofasciculus chthonoplastes exhibit distinct 24-hour transcriptional patterns, indicating differential circadian clock regulation.
• The observed differences suggest that the circadian clocks of these cyanobacteria have adapted to unique life strategies within microbial mats.
• Environmental conditions play a critical role in modulating circadian gene expression in these mat-forming cyanobacteria.