Reduction-dependent siderophore assimilation in a model pennate diatom

Proc Natl Acad Sci U S A. 2019 Nov 19;116(47):23609-23617. doi: 10.1073/pnas.1907234116. Epub 2019 Nov 4.


Iron uptake by diatoms is a biochemical process with global biogeochemical implications. In large regions of the surface ocean diatoms are both responsible for the majority of primary production and frequently experiencing iron limitation of growth. The strategies used by these phytoplankton to extract iron from seawater constrain carbon flux into higher trophic levels and sequestration into sediments. In this study we use reverse genetic techniques to target putative iron-acquisition genes in the model pennate diatom Phaeodactylum tricornutum We describe components of a reduction-dependent siderophore acquisition pathway that relies on a bacterial-derived receptor protein and provides a viable alternative to inorganic iron uptake under certain conditions. This form of iron uptake entails a close association between diatoms and siderophore-producing organisms during low-iron conditions. Homologs of these proteins are found distributed across diatom lineages, suggesting the significance of siderophore utilization by diatoms in the marine environment. Evaluation of specific proteins enables us to confirm independent iron-acquisition pathways in diatoms and characterize their preferred substrates. These findings refine our mechanistic understanding of the multiple iron-uptake systems used by diatoms and help us better predict the influence of iron speciation on taxa-specific iron bioavailability.

Keywords: diatom; ferric reductase; iron acquisition; phytoplankton; siderophore.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacterial Outer Membrane Proteins / metabolism*
  • Biological Availability
  • Biological Transport
  • CRISPR-Cas Systems
  • Climate Change
  • Diatoms / genetics
  • Diatoms / growth & development
  • Diatoms / metabolism*
  • FMN Reductase / genetics
  • FMN Reductase / metabolism*
  • Gallium / metabolism
  • Gene Knockout Techniques
  • Iron / metabolism*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Microbiota
  • Oxidation-Reduction
  • Phylogeny
  • Receptors, Cell Surface / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Seawater / chemistry
  • Siderophores / metabolism*
  • Species Specificity


  • Bacterial Outer Membrane Proteins
  • Membrane Transport Proteins
  • Receptors, Cell Surface
  • Recombinant Fusion Proteins
  • Siderophores
  • siderophore receptors
  • Gallium
  • Iron
  • FMN Reductase
  • ferric citrate iron reductase