Probing the bioavailability of organically bound iron: a case study in the Synechococcus-rich waters of the Gulf of Aqaba

Lis, Hagar; Shaked, Yeala

doi:10.3354/ame01347

Cited by 22 publications

(20 citation statements)

References 54 publications

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“…The surprising similarity of S.A. normalized Fe 0 uptake between cyanobacteria and eukaryotic phytoplankton ( Figure 5) implies that similar factors may be responsible for the upper limit on Fe uptake in both. Indeed, recent studies support the presence of a reductive step in Fe 0 uptake by Fe-limited cyanobacteria (Salmon et al, 2006;Lis and Shaked, 2009;Kranzler et al, 2011;Kranzler et al, 2014). This is consistent with the idea that the upper limit to iron uptake is fixed by the same maximum in the rate of Fe(III) reduction per S.A. as in eukaryotic phytoplankton.…”

Section: Discussionsupporting

confidence: 77%

“…Reductive Fe uptake involves an integral reductive step before internalization of Fe via the cell plasma membrane. This prevalent pathway has been demonstrated in the uptake of Fe 0 and organically bound Fe compounds in fresh water and marine prokaryotic and eukaryotic phytoplankton (Allnutt and Bonner, 1987;Jones et al, 1987;Eckhardt and Buckhout, 1998;Maldonado and Price, 2001;Lis and Shaked, 2009;Kranzler et al, 2011). Siderophoremediated Fe uptake involves direct transport of the ferric-siderophore complex into the cell where Fe is released from the chelating ligand.…”

Section: Introductionmentioning

confidence: 95%

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Iron bioavailability to phytoplankton: an empirical approach

et al. 2014

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Phytoplankton are often limited by iron in aquatic environments. Here we examine Fe bioavailability to phytoplankton by analyzing iron uptake from various Fe substrates by several species of phytoplankton grown under conditions of Fe limitation and comparing the measured uptake rate constants (Fe uptake rate/ substrate concentration). When unchelated iron, Fe 0 , buffered by an excess of the chelating agent EDTA is used as the Fe substrate, the uptake rate constants of all the eukaryotic phytoplankton species are tightly correlated and proportional to their respective surface areas (S.A.). The same is true when FeDFB is the substrate, but the corresponding uptake constants are one thousand times smaller than for Fe 0 . The uptake rate constants for the other substrates we examined fall mostly between the values for Fe 0 and FeDFB for the same S.A. These two model substrates thus empirically define a bioavailability envelope with Fe 0 at the upper and FeDFB at the lower limit of iron bioavailability. This envelope provides a convenient framework to compare the relative bioavailabilities of various Fe substrates to eukaryotic phytoplankton and the Fe uptake abilities of different phytoplankton species. Compared with eukaryotic species, cyanobacteria have similar uptake constants for Fe 0 but lower ones for FeDFB. The unique relationship between the uptake rate constants and the S.A. of phytoplankton species suggests that the uptake rate constant of Fe-limited phytoplankton has reached a universal upper limit and provides insight into the underlying uptake mechanism.

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Section: Discussionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 95%

Iron bioavailability to phytoplankton: an empirical approach

et al. 2014

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“…Calculations suggest that this pool should support partial growth of cyanobacteria in even the most iron-depleted oceanic regions 14 . Furthermore, one of the organisms in the HRG set, Synechococcus WH8102, may be able to reduce Fe(III)-siderophore complexes, thereby increasing the pool of unchelated iron for uptake 15 , although the molecular identity of the reductase is unknown.…”

Section: Genomic and Functional Characterizationmentioning

confidence: 99%

Genomic and functional adaptation in surface ocean planktonic prokaryotes

Yooseph

Nealson

Rusch

et al. 2010

Nature

279

261

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The understanding of marine microbial ecology and metabolism has been hampered by the paucity of sequenced reference genomes. To this end, we report the sequencing of 137 diverse marine isolates collected from around the world. We analysed these sequences, along with previously published marine prokaryotic genomes, in the context of marine metagenomic data, to gain insights into the ecology of the surface ocean prokaryotic picoplankton (0.1-3.0 mm size range). The results suggest that the sequenced genomes define two microbial groups: one composed of only a few taxa that are nearly always abundant in picoplanktonic communities, and the other consisting of many microbial taxa that are rarely abundant. The genomic content of the second group suggests that these microbes are capable of slow growth and survival in energy-limited environments, and rapid growth in energy-rich environments. By contrast, the abundant and cosmopolitan picoplanktonic prokaryotes for which there is genomic representation have smaller genomes, are probably capable of only slow growth and seem to be relatively unable to sense or rapidly acclimate to energy-rich conditions. Their genomic features also lead us to propose that one method used to avoid predation by viruses and/or bacterivores is by means of slow growth and the maintenance of low biomass. Molecular taxonomy and phylogeny1 revitalized the field of marine microbiology, allowing for the first time the realization that the 'unseen' and 'unknown' majority of uncultivated microbial taxa could be identified by their 16S ribosomal RNA genes, and identifying widespread clades of marine bacteria and archaea that had no cultivated representatives 2 . More recently, metagenomics has revealed the extent of diversity not fully explained using the available genomes of cultivated marine microbes. When the Sorcerer II Global Ocean Sampling (GOS) expedition metagenomic data were published 3,4 , it was remarkable in its duality of diversity. On the one hand, there seemed to be only a few taxonomic groups that appeared routinely in marine surface water samples. Of these groups, only three (Pelagibacter, Prochlorococcus and Synechococcus) were represented by cultivated marine microbes. On the other hand, despite their apparent ubiquity and abundance in the surface ocean, there was virtually no complete or near-complete genomic assembly of any of the cosmopolitan taxa, implying that these groups, as judged by 16S rRNA sequence, are internally extremely diverse. The GOS data set was also remarkable because of its apparent lack of relatedness to the entire collection of sequenced genomes: using a process called fragment recruitment, which is akin to in silico DNA hybridization, only a few genomes from the entire repertoire of sequenced genomes were found to have a significant number of GOS reads assigned to them.Here we use a large collection of sequenced marine genomes and metagenomic data to show the presence of two major groups in the marine surface picoplankton with striking differences in their met...

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“…Among cyanobacteria, the analysis of both laboratory cultures and natural populations suggested the existence of a reductive iron uptake pathway (Rose and Waite, 2005;Lis and Shaked, 2009). In a previous work we demonstrated that the unicellular cyanobacterium, Synechocystis sp.…”

Section: Introductionmentioning

confidence: 99%

Coordinated transporter activity shapes high-affinity iron acquisition in cyanobacteria

et al. 2013

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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.

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Probing the bioavailability of organically bound iron: a case study in the Synechococcus-rich waters of the Gulf of Aqaba

Cited by 22 publications

References 54 publications

Iron bioavailability to phytoplankton: an empirical approach

Iron bioavailability to phytoplankton: an empirical approach

Genomic and functional adaptation in surface ocean planktonic prokaryotes

Coordinated transporter activity shapes high-affinity iron acquisition in cyanobacteria

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