Coordinated transporter activity shapes high-affinity iron acquisition in cyanobacteria

Chana Kranzler*, Hagar Lis, Omri M. Finkel, Georg Schmetterer, Yeala Shaked, Nir Keren

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

Iron bioavailability limits biological activity in many aquatic and terrestrial environments. Broad scale genomic meta-analyses indicated that within a single organism, multiple iron transporters may contribute to iron acquisition. Here, we present a functional characterization of a cyanobacterial iron transport pathway that utilizes concerted transporter activities. Cyanobacteria are significant contributors to global primary productivity with high iron demands. Certain cyanobacterial species employ a siderophore-mediated uptake strategy; however, many strains possess neither siderophore biosynthesis nor siderophore transport genes. The unicellular, planktonic, freshwater cyanobacterium, Synechocystis sp. PCC 6803, employs an alternative to siderophore-based uptake-reduction of Fe(III) species before transport through the plasma membrane. In this study, we combine short-term radioactive iron uptake and reduction assays with a range of disruption mutants to generate a working model for iron reduction and uptake in Synechocystis sp. PCC 6803. We found that the Fe(II) transporter, FeoB, is the major iron transporter in this organism. In addition, we uncovered a link between a respiratory terminal oxidase (Alternate Respiratory Terminal Oxidase) and iron reduction - suggesting a coupling between these two electron transfer reactions. Furthermore, quantitative RNA transcript analysis identified a function for subunits of the Fe(III) transporter, FutABC, in modulating reductive iron uptake. Collectively, our results provide a molecular basis for a tightly coordinated, high-affinity iron transport system.

Original languageAmerican English
Pages (from-to)409-417
Number of pages9
JournalISME Journal
Volume8
Issue number2
DOIs
StatePublished - 26 Feb 2014

Bibliographical note

Funding Information:
We thank Terou Ogawa for generously sharing mutant strains with us. This work was supported by the Israeli Science Foundation (grant no. 806/11). GS acknowledges financial support from ‘Projekt Chlorophyll’.

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