Reduction-dependent siderophore assimilation in a model pennate diatom

Area of Science:

• Marine biology
• Biogeochemistry
• Phytoplankton physiology

Background:

• Diatoms are key primary producers in the ocean, often limited by iron availability.
• Iron uptake strategies by diatoms significantly influence global carbon and nutrient cycles.
• Understanding these strategies is vital for predicting oceanic responses to environmental changes.

Purpose of the Study:

• To investigate novel iron acquisition pathways in the diatom *Phaeodactylum tricornutum*.
• To characterize the mechanisms and significance of siderophore utilization by diatoms.
• To elucidate the diversity and substrate preferences of diatom iron uptake systems.

Main Methods:

• Utilized reverse genetics to target putative iron-acquisition genes in *Phaeodactylum tricornutum*.
• Described components of a reduction-dependent siderophore acquisition pathway.
• Analyzed homologs of identified proteins across various diatom lineages.

Main Results:

• Identified a reduction-dependent siderophore acquisition pathway dependent on a bacterial-derived receptor.
• Demonstrated siderophore uptake as a viable alternative to inorganic iron acquisition under iron-limited conditions.
• Confirmed the existence of independent iron acquisition pathways in diatoms and characterized their substrate specificities.

Conclusions:

• Diatoms possess multiple, distinct iron uptake systems, including a novel siderophore pathway.
• Siderophore utilization suggests a symbiotic relationship between diatoms and siderophore-producing organisms in low-iron environments.
• These findings enhance our understanding of iron bioavailability and its impact on marine ecosystems.