A unique porin meditates iron-selective transport through cyanobacterial outer membranes

Guo Wei Qiu, Hai Bo Jiang, Hagar Lis, Zheng Ke Li, Bin Deng, Jin Long Shang, Chuan Yu Sun, Nir Keren*, Bao Sheng Qiu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Cyanobacteria are globally important primary producers and nitrogen fixers with high iron demands. Low ambient dissolved iron concentrations in many aquatic environments mean that these organisms must maintain sufficient and selective transport of iron into the cell. However, the nature of iron transport pathways through the cyanobacterial outer membrane remains obscure. Here we present multiple lines of experimental evidence that collectively support the existence of a novel class of substrate-selective iron porin, Slr1908, in the outer membrane of the cyanobacterium Synechocystis sp. PCC 6803. Elemental composition analysis and short-term iron uptake assays with mutants in Slr1908 reveal that this protein is primarily involved in inorganic iron uptake and contributes less to the accumulation of other metals. Homologues of Slr1908 are widely distributed in both freshwater and marine cyanobacteria, most notably in unicellular marine diazotrophs. Complementary experiments with a homologue of Slr1908 in Synechococcus sp. PCC 7002 restored the phenotype of Synechocystis knockdown mutants, showing that this siderophore producing species also possesses a porin with a similar function in Fe transport. The involvement of a substrate-selective porins in iron uptake may allow cyanobacteria to tightly control iron flux into the cell, particularly in environments where iron concentrations fluctuate.

Original languageAmerican English
Pages (from-to)376-390
Number of pages15
JournalEnvironmental Microbiology
Issue number1
StatePublished - Jan 2021

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© 2020 Society for Applied Microbiology and John Wiley & Sons Ltd


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