Metabolic relationships between marine red algae and algae-associated bacteria

Area of Science:

• Marine microbiology
• Algal biotechnology
• Symbiotic interactions

Background:

• Marine phototrophs rely on mutualistic bacterial associations for survival.
• Metabolic exchanges between algae and bacteria are crucial but poorly understood.
• Bacterial communities associated with marine red algae were investigated.

Purpose of the Study:

• To analyze bacterial communities in marine red algal cultures.
• To investigate the metabolic capabilities of key associated bacteria (Roseibium and Phycisphaera).
• To elucidate the metabolic interactions between Roseibium and Porphyridium purpureum.

Main Methods:

• Analysis of bacterial communities in algal sphere and bulk solution.
• Bioinformatic analysis of Roseibium RMAR6-6 and Phycisphaera MAG 12 genomes.
• Comparative analysis with Porphyridium purpureum CCMP1328 genome.
• Transcriptomic analysis of monocultures and co-cultures.

Main Results:

• Roseibium and Phycisphaera were more abundant in the algal sphere.
• Roseibium RMAR6-6 possesses genes for nitrogen fixation, B vitamin production, and DMSP synthesis, benefiting the alga.
• Phycisphaera MAG 12 showed limited metabolic capabilities but could produce bacitracin.
• Nitrogen fixation and DMSP production by Roseibium promoted algal growth and reduced oxidative stress.

Conclusions:

• Roseibium RMAR6-6 significantly contributes to Porphyridium purpureum growth through nitrogen fixation and DMSP production.
• Metabolic interactions between Roseibium and Porphyridium purpureum were confirmed via transcriptomics.
• This study enhances understanding of marine algal-bacterial metabolic relationships for improved algal cultivation.