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A Comparative Study of Iron Uptake Rates and Mechanisms amongst Marine and Fresh Water Cyanobacteria: Prevalence of Reductive Iron Uptake.

Lis H, Kranzler C, Keren N, Shaked Y - Life (Basel) (2015)

Bottom Line: Uniformity in kin/SA suggests similarity in the mechanism of uptake and indeed, all strains were found to employ a reductive step in the uptake of Fe' and FOB.In contrast, different uptake pathways were found for FeAB along with variations in kin/SA.Cyanobacteria combining both uptake strategies benefit from increased flexibility in accessing different Fe-substrates.

View Article: PubMed Central - PubMed

Affiliation: Interuniversity Institute for Marine Sciences in Eilat, Israel. hagarlis@gmail.com.

ABSTRACT
In this contribution, we address the question of iron bioavailability to cyanobacteria by measuring Fe uptake rates and probing for a reductive uptake pathway in diverse cyanobacterial species. We examined three Fe-substrates: dissolved inorganic iron (Fe') and the Fe-siderophores Ferrioxamine B (FOB) and FeAerobactin (FeAB). In order to compare across substrates and strains, we extracted uptake rate constants (kin = uptake rate/[Fe-substrate]). Fe' was the most bioavailable Fe form to cyanobacteria, with kin values higher than those of other substrates. When accounting for surface area (SA), all strains acquired Fe' at similar rates, as their kin/SA were similar. We also observed homogeneity in the uptake of FOB among strains, but with 10,000 times lower kin/SA values than Fe'. Uniformity in kin/SA suggests similarity in the mechanism of uptake and indeed, all strains were found to employ a reductive step in the uptake of Fe' and FOB. In contrast, different uptake pathways were found for FeAB along with variations in kin/SA. Our data supports the existence of a common reductive Fe uptake pathway amongst cyanobacteria, functioning alone or in addition to siderophore-mediated uptake. Cyanobacteria combining both uptake strategies benefit from increased flexibility in accessing different Fe-substrates.

No MeSH data available.


Related in: MedlinePlus

A comparison of FOB and Fe' uptake by iron limited cyanobacteria. (a) Uptake rate constant (kin = uptake rate/ [Fe-substrate]) as a function of cell surface area on a log-log plot. Linear regression analysis on Fe' includes only marine strains, while that for FOB includes all strains; (b) Species-specific FOB uptake data. In order to compare between species, we normalized the uptake rate constant to cell surface area (i.e., kin/S.A.). The dashed lines indicate the average kin/SA of Fe' and FOB uptake for all species i.e., the slope of the Fe' and FOB trend lines in Figure A. Uptake rates were normalized to per cell for Anabaena and Prochlorococcus using conversion factors of 158 and 1.4 fg·Chl-a·cell−1, respectively.
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life-05-00841-f004: A comparison of FOB and Fe' uptake by iron limited cyanobacteria. (a) Uptake rate constant (kin = uptake rate/ [Fe-substrate]) as a function of cell surface area on a log-log plot. Linear regression analysis on Fe' includes only marine strains, while that for FOB includes all strains; (b) Species-specific FOB uptake data. In order to compare between species, we normalized the uptake rate constant to cell surface area (i.e., kin/S.A.). The dashed lines indicate the average kin/SA of Fe' and FOB uptake for all species i.e., the slope of the Fe' and FOB trend lines in Figure A. Uptake rates were normalized to per cell for Anabaena and Prochlorococcus using conversion factors of 158 and 1.4 fg·Chl-a·cell−1, respectively.

Mentions: Similarly to Fe' uptake, the uptake constants (kin) of FOB (where kin = uptake rate/[FOB]), are linearly correlated to cell surface area for a range of species (Figure 4a). Figure 4b summarizes the surface area normalized uptake rate constants (in units of L μm−2·h−1) of a range of cyanobacterial species from the current study as well as previously published works and emphasizes the appreciable similarity in FOB kin/S.A. values across different cyanobacterial strains. For both Fe' and FOB all experimental cyanobacterial strains fall along a linear regression line (Figure 4a). Therefore, we can extract the slope of the two trend lines defining Fe' and FOB uptake in order to compare the bioavailability of these two substrates on a cell surface area basis. The average FOB kin/S.A. value as indicated by the slope of the linear trend line (6.3 × 10−15 L·μm−2·h−1) is four orders of magnitude lower than that for Fe' (7.21 × 10−11 L·μm−2·h−1). A summary of all measured 55FOB uptake rate constants can be found in the supplemental (Table S3).


A Comparative Study of Iron Uptake Rates and Mechanisms amongst Marine and Fresh Water Cyanobacteria: Prevalence of Reductive Iron Uptake.

Lis H, Kranzler C, Keren N, Shaked Y - Life (Basel) (2015)

A comparison of FOB and Fe' uptake by iron limited cyanobacteria. (a) Uptake rate constant (kin = uptake rate/ [Fe-substrate]) as a function of cell surface area on a log-log plot. Linear regression analysis on Fe' includes only marine strains, while that for FOB includes all strains; (b) Species-specific FOB uptake data. In order to compare between species, we normalized the uptake rate constant to cell surface area (i.e., kin/S.A.). The dashed lines indicate the average kin/SA of Fe' and FOB uptake for all species i.e., the slope of the Fe' and FOB trend lines in Figure A. Uptake rates were normalized to per cell for Anabaena and Prochlorococcus using conversion factors of 158 and 1.4 fg·Chl-a·cell−1, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390881&req=5

life-05-00841-f004: A comparison of FOB and Fe' uptake by iron limited cyanobacteria. (a) Uptake rate constant (kin = uptake rate/ [Fe-substrate]) as a function of cell surface area on a log-log plot. Linear regression analysis on Fe' includes only marine strains, while that for FOB includes all strains; (b) Species-specific FOB uptake data. In order to compare between species, we normalized the uptake rate constant to cell surface area (i.e., kin/S.A.). The dashed lines indicate the average kin/SA of Fe' and FOB uptake for all species i.e., the slope of the Fe' and FOB trend lines in Figure A. Uptake rates were normalized to per cell for Anabaena and Prochlorococcus using conversion factors of 158 and 1.4 fg·Chl-a·cell−1, respectively.
Mentions: Similarly to Fe' uptake, the uptake constants (kin) of FOB (where kin = uptake rate/[FOB]), are linearly correlated to cell surface area for a range of species (Figure 4a). Figure 4b summarizes the surface area normalized uptake rate constants (in units of L μm−2·h−1) of a range of cyanobacterial species from the current study as well as previously published works and emphasizes the appreciable similarity in FOB kin/S.A. values across different cyanobacterial strains. For both Fe' and FOB all experimental cyanobacterial strains fall along a linear regression line (Figure 4a). Therefore, we can extract the slope of the two trend lines defining Fe' and FOB uptake in order to compare the bioavailability of these two substrates on a cell surface area basis. The average FOB kin/S.A. value as indicated by the slope of the linear trend line (6.3 × 10−15 L·μm−2·h−1) is four orders of magnitude lower than that for Fe' (7.21 × 10−11 L·μm−2·h−1). A summary of all measured 55FOB uptake rate constants can be found in the supplemental (Table S3).

Bottom Line: Uniformity in kin/SA suggests similarity in the mechanism of uptake and indeed, all strains were found to employ a reductive step in the uptake of Fe' and FOB.In contrast, different uptake pathways were found for FeAB along with variations in kin/SA.Cyanobacteria combining both uptake strategies benefit from increased flexibility in accessing different Fe-substrates.

View Article: PubMed Central - PubMed

Affiliation: Interuniversity Institute for Marine Sciences in Eilat, Israel. hagarlis@gmail.com.

ABSTRACT
In this contribution, we address the question of iron bioavailability to cyanobacteria by measuring Fe uptake rates and probing for a reductive uptake pathway in diverse cyanobacterial species. We examined three Fe-substrates: dissolved inorganic iron (Fe') and the Fe-siderophores Ferrioxamine B (FOB) and FeAerobactin (FeAB). In order to compare across substrates and strains, we extracted uptake rate constants (kin = uptake rate/[Fe-substrate]). Fe' was the most bioavailable Fe form to cyanobacteria, with kin values higher than those of other substrates. When accounting for surface area (SA), all strains acquired Fe' at similar rates, as their kin/SA were similar. We also observed homogeneity in the uptake of FOB among strains, but with 10,000 times lower kin/SA values than Fe'. Uniformity in kin/SA suggests similarity in the mechanism of uptake and indeed, all strains were found to employ a reductive step in the uptake of Fe' and FOB. In contrast, different uptake pathways were found for FeAB along with variations in kin/SA. Our data supports the existence of a common reductive Fe uptake pathway amongst cyanobacteria, functioning alone or in addition to siderophore-mediated uptake. Cyanobacteria combining both uptake strategies benefit from increased flexibility in accessing different Fe-substrates.

No MeSH data available.


Related in: MedlinePlus