Ectoine from Bacterial and Algal Origin Is a Compatible Solute in Microalgae.

Area of Science:

• Marine Biology
• Biochemistry
• Microbiology

Background:

• Phytoplankton osmoregulation relies on polar metabolites, with dimethylsulfoniopropionate (DMSP) traditionally considered dominant.
• Ectoine, a known bacterial compatible solute, has not been previously identified as a phytoplankton osmolyte.

Purpose of the Study:

• To identify novel osmolytes in phytoplankton.
• To investigate the origin and role of ectoine in microalgae osmoadaptation.
• To explore the interplay between bacteria and algae in metabolite production.

Main Methods:

• Optimized extraction and detection of polar metabolites in microalgae.
• Analysis of ectoine concentrations in xenic and axenic algal cultures.
• Cultivation of model diatoms under varying salinity conditions (35 PSU vs. 50 PSU).

Main Results:

• Ectoine was identified as a significant osmolyte in several microalgae species.
• Elevated ectoine levels were observed in microalgae cultures harboring associated bacteria, suggesting a dual origin (biosynthesis and uptake).
• Ectoine concentrations increased in diatoms grown at higher salinity (50 PSU) compared to standard conditions (35 PSU).

Conclusions:

• Ectoine is confirmed as an osmoadaptive metabolite in phytoplankton.
• Microalgae exhibit ectoine biosynthesis and/or uptake from associated bacteria.
• A synergistic metabolic relationship between bacteria and algae in osmoregulation is proposed.