Haematococcus pluvialis microzooid and palmella cells display distinct metabolic responses to excess manganese

Area of Science:

• * Environmental microbiology
• * Phycology
• * Biochemistry

Background:

• * Haematococcus pluvialis is a commercially significant microalga with a complex life cycle, complicating stress response studies.
• * Manganese (Mn) is vital but toxic in excess, necessitating understanding of algal tolerance mechanisms.
• * Limited knowledge exists on microalgal metabolism and adaptation to environmental stressors like manganese.

Purpose of the Study:

• * To investigate the metabolic and cellular responses of Haematococcus pluvialis to high, sub-lethal manganese concentrations.
• * To differentiate stress responses between motile microzooids and non-motile palmella cells.
• * To elucidate the biochemical mechanisms of manganese management in H. pluvialis.

Main Methods:

• * Coupled high-resolution elemental imaging, spectroscopy, and microscopy.
• * Metabolic profiling techniques.
• * Comparative analysis of microzooid and palmella cell responses to manganese stress.

Main Results:

• * Microzooids exhibited vacuolisation, cell wall changes, and Mn internalization, alongside upregulated protein synthesis and depleted lipids.
• * Palmella cells showed less vacuolisation with Mn localized near storage granules, indicating higher manganese tolerance.
• * Mn sequestration involved intracellular sulphate moieties and cell wall carboxyl groups in microzooids.

Conclusions:

• * Haematococcus pluvialis employs distinct strategies for manganese management, differing between life stages.
• * Microzooids demonstrate active Mn detoxification and metabolic adjustments, while palmella cells show greater resilience.
• * Understanding these biochemical mechanisms is crucial for optimizing microalgal cultivation and biotechnological applications.