Extracellular polysaccharide production by thraustochytrid protists

Area of Science:

• Marine microbiology
• Protistology
• Biochemistry

Background:

• Thraustochytrids are marine stramenopilan protists.
• Extracellular polysaccharides (EPSs) are polymers secreted by cells.
• The role of EPSs in thraustochytrid physiology is not fully understood.

Purpose of the Study:

• To investigate the production of extracellular polysaccharides (EPSs) by marine thraustochytrids.
• To characterize the composition and properties of thraustochytrid EPSs.
• To explore the potential function of EPSs in cell survival.

Main Methods:

• Cultivation of four thraustochytrid strains.
• Microscopy (light and scanning electron) for EPS visualization.
• Quantification of EPS in culture filtrates.
• Anion exchange chromatography for EPS fractionation.
• Biochemical analysis of EPS composition (sugars, proteins, lipids, uronic acids, sulfates).
• Molecular weight determination of EPS.
• Desiccation survival assays.

Main Results:

• EPS matrix observed around cell groups in stationary cultures.
• EPS yield in shake cultures ranged from 0.3 to 1.1 g/L.
• EPS production peaked in the stationary phase and increased with culture age.
• EPS composition: 39-53% sugars, proteins, lipids, uronic acids, sulfates.
• Molecular weights of EPS: ~94 kDa (SC-1) and ~320 kDa (CW1).
• Glucose was the major sugar component.
• Thraustochytrid cultures survived 96 hours of air-drying.

Conclusions:

• Thraustochytrids actively produce and secrete EPS.
• EPS production is influenced by culture conditions and age.
• Thraustochytrid EPS is a complex mixture of carbohydrates and other molecules.
• EPS likely plays a crucial role in protecting thraustochytrid cells against desiccation.