Carbohydrate formation in rewetted terrestrial cyanobacteria

Area of Science:

• Microbiology
• Plant Physiology
• Biochemistry

Background:

• Terrestrial cyanobacteria like Nostoc commune survive desiccation by forming mats.
• Carbohydrate polymers play crucial roles in cellular function and structural integrity.

Purpose of the Study:

• To investigate carbohydrate polymer formation and metabolism in Nostoc commune mats upon rewetting.
• To differentiate between storage carbohydrates and sheath material.
• To understand the role of carbohydrates in the recovery of terrestrial cyanobacteria.

Main Methods:

• Measurement of total carbohydrates as anthrone-reactive material (ARM).
• Enzymic assay for storage carbohydrate (glycogen).
• Analysis under a light-dark regime after rewetting desiccated mats.

Main Results:

• Glycogen constituted less than one-tenth of ARM in dry thalli.
• Rewetting and illumination increased total carbohydrates, with glycogen showing cyclical synthesis and degradation.
• Submerged illuminated colonies showed glycogen hydrolysis, suggesting its use in cellular recovery.
• Photosynthesis supported net glycogen synthesis only under sufficient aeration.

Conclusions:

• The majority of ARM in Nostoc commune is inert sheath material, crucial for water retention.
• Glycogen serves as a dynamic storage carbohydrate, vital for rapid recovery after rewetting.
• Photosynthesis and aeration are key factors for glycogen synthesis in terrestrial cyanobacteria.