Iron transporters in marine prokaryotic genomes and metagenomes

Summary In the pelagic environment, iron is a scarce but essential micronutrient. The iron acquisition capabilities of selected marine bacteria have been investigated, but the recent proliferation of marine prokaryotic genomes and metagenomes offers a more comprehensive picture of microbial iron uptake pathways in the ocean. Searching these data sets, we were able to identify uptake mechanisms for Fe 3+ , Fe 2+ and iron chelates (e.g. siderophore and haem iron complexes). Transport of iron chelates is accomplished by TonB‐dependent transporters (TBDTs). After clustering the TBDTs from marine prokaryotic genomes, we identified TBDT clusters for the transport of hydroxamate and catecholate siderophore iron complexes and haem using gene neighbourhood analysis and co‐clustering of TBDTs of known function. The genomes also contained two classes of siderophore biosynthesis genes: NRPS (non‐ribosomal peptide synthase) genes and NIS (NRPS Independent Siderophore) genes. The most common iron transporters, in both the genomes and metagenomes, were Fe 3+