Enhanced ferrihydrite dissolution by a unicellular, planktonic cyanobacterium: a biological contribution to particulate iron bioavailability

Chana Kranzler*, Nivi Kessler, Nir Keren, Yeala Shaked

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Iron (Fe) bioavailability, as determined by its sources, sinks, solubility and speciation, places severe environmental constraints on microorganisms in aquatic environments. Cyanobacteria are a widespread group of aquatic, photosynthetic microorganisms with especially high iron requirements. While iron exists predominantly in particulate form, little is known about its bioavailability to cyanobacteria. Some cyanobacteria secrete iron solubilizing ligands called siderophores, yet many environmentally relevant strains do not have this ability. This work explores the bioavailability of amorphous synthetic Fe-oxides (ferrihydrite) to the non-siderophore producing, unicellular cyanobacterium, Synechocystis sp PCC 6803. Iron uptake assays with 55ferrihydrite established dissolution as a critical prerequisite for iron transport. Dissolution assays with the iron binding ligand, desferrioxamine B, demonstrated that Synechocystis 6803 enhances ferrihydrite dissolution, exerting siderophore-independent biological influence on ferrihydrite bioavailability. Dissolution mechanisms were studied using a range of experimental conditions; both cell-particle physical proximity and cellular electron flow were shown to be important determinants of bio-dissolution by Synechocystis 6803. Finally, the effects of ferrihydrite stability on bio-dissolution rates and cell physiology were measured, integrating biological and chemical aspects of ferrihydrite bioavailability. Collectively, these findings demonstrate that Synechocystis 6803 actively dissolves ferrihydrite, highlighting a significant biological component to mineral phase iron bioavailability in aquatic environments.

Original languageAmerican English
Pages (from-to)5101-5111
Number of pages11
JournalEnvironmental Microbiology
Volume18
Issue number12
DOIs
StatePublished - 1 Dec 2016

Bibliographical note

Publisher Copyright:
© 2016 Society for Applied Microbiology and John Wiley & Sons Ltd

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