Outer Membrane Iron Uptake Pathways in the Model Cyanobacterium Synechocystis sp. Strain PCC 6803

Qiu, Guo-Wei; Lou, Wenjing; Sun, Chuanyu; Yang, Ning; Li, Zheng‐Ke; Li, Ding-Lan; Zang, Shasha; Fu, Fei-Xue; Hutchins, David A.; Jiang, Haibo; Qiu, Bao‐Sheng

doi:10.1128/aem.01512-18

Cited by 33 publications

(64 citation statements)

References 57 publications

(84 reference statements)

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“…Genes encoding components of siderophore synthesis are absent in this species (Hopkinson and Morel, 2009), but it is able to use siderophores produced by other organisms, such as FOB, schizokinen, aerobactin (Kranzler et al, 2011) or hydroxamate siderophores produced by the cyanobacterium Anabaena variabilis ATCC 29413 (Babykin et al, 2018;Obando et al, 2018). One TonB protein and four TBDTs are present in Synechocystis 6803, and expression of the TonB gene and of the TBDT-encoding genes was induced by iron limitation (Qiu et al, 2018). Moreover, a mutant disrupted for the TonB gene showed defective growth on low iron medium, and a quadruple mutant in which the four TBDTs were inactivated showed induction of iron uptake genes such as futA and feoB (Qiu et al, 2018).…”

Section: Synechocystis Sp Strain Pcc 6803 As a Model Cyanobacteriummentioning

confidence: 98%

“…Ferrous iron would then be transported into the cell by the FeoB protein and/or by divalent metal ion transporters (NRAMP or ZIP transporters for picocyanobacteria) (Hopkinson and Barbeau, 2012). Iron may be transported across the outer membrane to the periplasm by an active mechanism mediated by a TBDT, or a passive diffusion mechanism mediated by porins, which are trimeric outer membrane β-barrel proteins (Qiu et al, 2018). When it reaches the periplasm, ferric iron is bound by FutA2, generating a chemical gradient to facilitate iron influx (Kranzler et al, 2014).…”

Section: Reductive Iron Uptake and Uptake Of Inorganic Ferric Speciesmentioning

confidence: 99%

“…One TonB protein and four TBDTs are present in Synechocystis 6803, and expression of the TonB gene and of the TBDT-encoding genes was induced by iron limitation (Qiu et al, 2018). Moreover, a mutant disrupted for the TonB gene showed defective growth on low iron medium, and a quadruple mutant in which the four TBDTs were inactivated showed induction of iron uptake genes such as futA and feoB (Qiu et al, 2018). The quadruple mutant also showed defective iron uptake from both siderophores (FOB) and inorganic ferric species (Fe'), although residual iron uptake was higher with Fe' as iron source, suggesting that Fe' could be taken up by another pathway (Qiu et al, 2018).…”

Section: Synechocystis Sp Strain Pcc 6803 As a Model Cyanobacteriummentioning

confidence: 99%

“…Moreover, a mutant disrupted for the TonB gene showed defective growth on low iron medium, and a quadruple mutant in which the four TBDTs were inactivated showed induction of iron uptake genes such as futA and feoB (Qiu et al, 2018). The quadruple mutant also showed defective iron uptake from both siderophores (FOB) and inorganic ferric species (Fe'), although residual iron uptake was higher with Fe' as iron source, suggesting that Fe' could be taken up by another pathway (Qiu et al, 2018). There are six porins expressed at the outer membrane of Synechocystis 6803, and it was shown (by generating mutants) that these porins were involved in residual Fe' uptake (Qiu et al, 2018).…”

Section: Synechocystis Sp Strain Pcc 6803 As a Model Cyanobacteriummentioning

confidence: 99%

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Iron Uptake Mechanisms in Marine Phytoplankton

2020

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Oceanic phytoplankton species have highly efficient mechanisms of iron acquisition, as they can take up iron from environments in which it is present at subnanomolar concentrations. In eukaryotes, three main models were proposed for iron transport into the cells by first studying the kinetics of iron uptake in different algal species and then, more recently, by using modern biological techniques on the model diatom Phaeodactylum tricornutum. In the first model, the rate of uptake is dependent on the concentration of unchelated Fe species, and is thus limited thermodynamically. Iron is transported by endocytosis after carbonate-dependent binding of Fe(III)' (inorganic soluble ferric species) to phytotransferrin at the cell surface. In this strategy the cells are able to take up iron from very low iron concentration. In an alternative model, kinetically limited for iron acquisition, the extracellular reduction of all iron species (including Fe') is a prerequisite for iron acquisition. This strategy allows the cells to take up iron from a great variety of ferric species. In a third model, hydroxamate siderophores can be transported by endocytosis (dependent on ISIP1) after binding to the FBP1 protein, and iron is released from the siderophores by FRE2-dependent reduction. In prokaryotes, one mechanism of iron uptake is based on the use of siderophores excreted by the cells. Iron-loaded siderophores are transported across the cell outer membrane via a TonB-dependent transporter (TBDT), and are then transported into the cells by an ABC transporter. Open ocean cyanobacteria do not excrete siderophores but can probably use siderophores produced by other organisms. In an alternative model, inorganic ferric species are transported through the outer membrane by TBDT or by porins, and are taken up by the ABC transporter system FutABC. Alternatively, ferric iron of the periplasmic space can be reduced by the alternative respiratory terminal oxidase (ARTO) and the ferrous ions can be transported by divalent metal transporters (FeoB or ZIP). After reoxidation, iron can be taken up by the high-affinity permease Ftr1.

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Section: Synechocystis Sp Strain Pcc 6803 As a Model Cyanobacteriummentioning

confidence: 98%

Section: Reductive Iron Uptake and Uptake Of Inorganic Ferric Speciesmentioning

confidence: 99%

Section: Synechocystis Sp Strain Pcc 6803 As a Model Cyanobacteriummentioning

confidence: 99%

Section: Synechocystis Sp Strain Pcc 6803 As a Model Cyanobacteriummentioning

confidence: 99%

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Iron Uptake Mechanisms in Marine Phytoplankton

2020

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“…A recent study has suggested that TBDRs of Synechocystis sp. PCC 6803 mediate the uptake of free iron, thereby not restricting iron uptake to only ferric-siderophore complexes 21 . The transport of ferrous iron across the inner membrane is mainly facilitated by Feo and divalent metal ion transporters such as MntH and ZupT 20 .…”

Section: Introductionmentioning

confidence: 99%

Iron acquisition system ofSphingobiumsp. strain SYK-6, a degrader of lignin-derived aromatic compounds

Fujita

Sakumoto

Tanatani

et al. 2020

Preprint

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23Iron, an essential element for all organisms, acts as a cofactor of enzymes in bacterial 24 degradation of recalcitrant aromatic compounds. The bacterial family, Sphingomonadaceae 25 comprises various degraders of recalcitrant aromatic compounds; however, little is known 26 about their iron acquisition system. Here, we investigated the iron acquisition system in a 27 model bacterium capable of degrading lignin-derived aromatics, Sphingobium sp. strain 28 SYK-6. Analyses of SYK-6 mutants revealed that FiuA (SLG_34550), a TonB-dependent 29 receptor (TBDR), was the major outer membrane iron transporter. Three other TBDRs 30 encoded by SLG_04340, SLG_04380, and SLG_10860 also participated in iron uptake, and 31 tonB2 (SLG_34550), one of the six tonB comprising the Ton complex which enables 32 TBDR-mediated transport was critical for iron uptake. The ferrous iron transporter FeoB 33 (SLG_36840) played an important role in iron uptake across the inner membrane. The 34 promoter activities of most of the iron uptake genes were induced under iron-limited 35 conditions, and their regulation is controlled by SLG_29410 encoding the ferric uptake 36 regulator, Fur. Although feoB, among all the iron uptake genes identified is highly conserved 37 in Sphingomonad strains, the outer membrane transporters seem to be diversified. Elucidation 38 of the iron acquisition system promises better understanding of the bacterial degradation 39 mechanisms of aromatic compounds.40 41 42Iron is an essential nutrient utilised as a cofactor for enzymes that control various life 43 phenomena such as respiration, dissimilation, and stress response 1 . Iron exists mainly in 44 ferrous and ferric forms. Ferrous iron is soluble and highly bioavailable; however, the 45 predominant form of iron in the environment is an insoluble ferric form 2 . Ferric iron in soil 46 and water is solubilised by forming complexes with organic ligands such as siderophores, 47 humic acid, lipids, proteins, and polysaccharides 3,4 . Many bacteria secrete specific 48 high-affinity siderophores which form complexes with ferric iron and then uptake these 49 ferric-siderophore complexes to enhance iron acquisition over competitors [5][6][7] . Besides, 50 pathogenic bacteria can acquire haem and transferrin specifically from their host cells 8,9 . 51 Gram-negative bacteria need to transport iron through both the outer and inner 52 membranes. TonB-dependent receptors (TBDRs) mediate transport of ferric complexes (e.g. 53 siderophore, haem, and transferrin) across the outer membrane 1,10,11 . TBDRs utilize energy 54 derived from the proton motive force transmitted by TonB-ExbB-ExbD complex (Ton 55 complex) localised in the inner membrane (Ton system) 12 . Beside siderophores, the Ton 56 system is involved in the uptake of vitamin B12, saccharide, aromatic compounds, and metals 57 such as nickel, copper, and lanthanoid [13][14][15][16][17][18] . The uptake of the ferric complex across the inner 58 membrane is mainly achieved by ATP-binding cassette (ABC) transporters 11...

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Adaptive Mechanisms of the Model Photosynthetic Organisms, Cyanobacteria, to Iron Deficiency

Jiang

Deng

et al. 2020

Microbial Photosynthesis

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Outer Membrane Iron Uptake Pathways in the Model Cyanobacterium Synechocystis sp. Strain PCC 6803

Cited by 33 publications

References 57 publications

Iron Uptake Mechanisms in Marine Phytoplankton

Iron Uptake Mechanisms in Marine Phytoplankton

Iron acquisition system ofSphingobiumsp. strain SYK-6, a degrader of lignin-derived aromatic compounds

Adaptive Mechanisms of the Model Photosynthetic Organisms, Cyanobacteria, to Iron Deficiency

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