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71.
72.
The role of mineral compounds and chemical conditions in the binding of phosphate in the Ems estuary
In the Ems estuary the gradients in dissolved phosphorus and iron are non-conservative and opposite. The relations between
different mineral compounds, environmental conditions and phosphate concentrations were studied, in an attempt to explain
this. Laboratory experiments on water samples from the reaches with high concentrations of phosphate and of suspended matter
revealed a low concentration of calcite-bound phosphorus in the middle reaches of the estuary (only 0.07%). Therefore, it
is concluded that calcite possibly plays only a modest role in phosphate distribution in the Ems estuary. Further experiments
revealed that nearly 70% of the particulate inorganic phosphorus is iron-bound. It is demonstrated that organic coatings on
minerals inhibit phosphate release at a low redox potential. Moreover, the organic matter itself contained c. 20% of particulate
phosphorus. Approximately 10% of the particulate phosphorus may be associated with clay minerals. It is concluded that in
addition to biological processes, the phosphorus associated with ironoxyhydroxides may be crucial for the seasonal variation
of the phosphate concentrations in the water. 相似文献
73.
74.
Holger Stephan Stefan Freund Werner Beck Günther Jung Jean-Marie Meyer Günther Winkelmann 《Biometals》1993,6(2):93-100
Novel linear hydroxamate/hydroxycarboxylate siderophores from strains of Pseudomonas cepacia were isolated and named ornibactins. The ornibactins represent modified tetrapeptide siderophores, possessing the sequence l-Orn1(N
-OH, N
-acyl)-d-threo-Asp(-OH)-l-Ser-l-Orn4(N
-OH, N
-formyl)-1,4-diaminobutane. The N
-acyl groups of Orn1(N
-OH, N
-acyl) may vary and represent the three acids 3-hydroxybutanoic acid, 3-hydroxyhexanoic acid and 3-hydroxyoctanoic acid, leading to a mixture of three different ornibactins, designated according to their acyl chain length as ornibactin-C4, ornibactin-C6 and ornibactin-C8. Each of the siderophores is accompanied by a small amount of a more hydrophilic component with a 16 a.m.u. higher mass. The structure elucidation was based on results from gas chromatography amino acid analysis, electrospray mass spectrometry, and one- and two-dimensional nuclear magnetic resonance techniques. 相似文献
75.
Kristofer M. Gomes Brook L. Nunn P. Dreux Chappell Bethany D. Jenkins 《Journal of phycology》2023,59(5):1085-1099
Diatoms are important primary producers in the world's oceans, yet their growth is constrained in large regions by low bioavailable iron (Fe). Low-Fe stress-induced limitation of primary production is due to requirements for Fe in components of essential metabolic pathways including photosynthesis and other chloroplast plastid functions. Studies have shown that under low-Fe stress, diatoms alter plastid-specific processes, including components of electron transport. These physiological changes suggest changes of protein content and in protein abundances within the diatom plastid. While in silico predictions provide putative information on plastid-localized proteins, knowledge of diatom plastid proteins remains limited in comparison to well-studied model photosynthetic organisms. To address this, we employed shotgun proteomics to investigate the proteome of subcellular plastid-enriched fractions from Thalassiosira pseudonana to gain a better understanding of how the plastid proteome is remodeled in response to Fe limitation. Using mass spectrometry-based peptide identification and quantification, we analyzed T. pseudonana grown under Fe-replete and -limiting conditions. Through these analyses, we inferred the relative quantities of each protein, revealing that Fe limitation regulates major metabolic pathways in the plastid, including the Calvin cycle. Additionally, we observed changes in the expression of light-harvesting proteins. In silico localization predictions of proteins identified in this plastid-enriched proteome allowed for an in-depth comparison of theoretical versus observed plastid-localization, providing evidence for the potential of additional protein import pathways into the diatom plastid. 相似文献
76.
Cultures of Trichodesmium NIBB 1067 were grown in the synthetic medium AQUIL with a range of iron added from none to 5 × 10?7 M Fe for 15 days. Chlorophyll-a, cell counts, and total cell volume were two or three times higher in medium with 10?7 M Fe than with no added Fe. Oxygen production rate per chlorophyll-a was over 60% higher with higher iron. Increased iron stimulated photosynthesis at all irradiances from about 12–250 μE · m?2· s?1. Nitrogen fixation rate, estimated from acetylene reduction, for 10?7 and 10?8 M Fe cultures was approximately twice that of the cultures with no added Fe. The range of rates of O2 production and N2 fixation in cultures at the iron concentrations we used were similar to the rates from natural samples of Trichodesmium from both the Atlantic, and the Pacific oceans. This similarity may allow this clone to be used, with some caution, for future physiological ecology studies. This study demonstrates the importance of iron to photosynthesis and nitrogen fixation and suggests that Trichodesmium plays a central role in the biogeochemical cycles of iron, carbon and nitrogen. 相似文献
77.
The influence of nicotianamine (NA) on formation and elongation of adventitious roots in hypocotyls of de-rooted NA-less mutant seedlings of Lycopersicon esculentum Mill, was examined in relation to the iron supply [ferric N-N'-ethylenediaminedi-(2-hydroxyphenylacetate) (FEDDHA), ferric ethylenediaminetetracetate (FeEDTA), ferric N-(2-hydroxyethyl)-ethylenediaminetriacetate (FeHEDTA, Fe-citrate and FeCl3 ] in the nutrient solution. The initiation of root primordia in hypocotyl cuttings was independent of NA and occurred with about the same frequency in both, mutant and wild-type. In the mutant the development of primordia to adventitious roots was blocked at all iron sources used, except FeEDTA. Addition of NA (5x 10−6 to 2 × 10−5 M ) to the rooting medium resulted in a fast growth of adventitious roots in mutant cuttings with all iron sources tested. Rooting of wild-type cuttings was independent from NA application and iron sources. We suppose that NA is involved in the intracellular transport of iron. Its function is possibly linked with chelation of ferrous iron in the cell. 相似文献
78.
A simple and rapid fl ow injection method is reported for the determination of iron in blood serum after acid digestion with HNO3 and HClO4, based on luminol CL detection in the absence of added oxidant. The detection limit (3 s) was 1.0 nmol/L with a sample throughput of 120/h. The calibration graph was linear over the range 0.001-1.0 micromol/L (r2 = 0.9974), with relative standard deviations (RSD) (n = 4) in the range 3.2-5%. The effect of interfering cations (Ca(II), Mg(II), Cu(II), Cd(II), Pb(II), Mn(II), Zn(II), Ni(II), Co(II) and Fe(III)) and anions (Cl-, SO4(2-), HCO3-, NO3-, NO2-) were studied using a luminol CL system for Fe(II) determination. The method was applied to normal blood serum and the results (1.32 +/- 0.08-1.74 +/- 0.05 mg/L) were compared with those from a spectrophotometric reference method (1.34 +/- 0.06-1.80 +/- 0.10 mg/L), which agree fairly well with the overall reference range in blood. 相似文献
79.
John G. Rueter 《Journal of phycology》1988,24(2):249-254
Iron availability may limit carbon and nitrogen fixation in the oceans. The freshwater cyanobacterium, Anabaena, was used as a laboratory model for the biochemical and physiological effects of iron. Increased iron nutrition, in the range of 10?8 M to 10?6 M resulted in increases of approximately four fold in carbon and nitrogen fixation rates. Chlorophyll concentration increased, and the relative amount of in vivo fluorescence was reduced with more iron. Natural samples of Trichodesmium, collected off Barbados and incubated with increased iron for two days, showed similar effects. Trichodesmium responded to iron additions indicating that it may be Fe limited in its natural environment. These responses to iron are consistent with the biochemical roles of iron in photosynthesis and nitrogen fixation. The results are discussed in the geochemical context of the sporadic total iron input to tropical oceans and possible implications to spatial and temporal patterns of productivity. 相似文献
80.
渗透胁迫下稻苗中铁催化的膜脂过氧化作用 总被引:12,自引:0,他引:12
在-0.7MPa渗透胁迫下,水稻幼苗体内和H2O2大量产生,Fe2+积累,膜脂过氧化作用加剧。水稻幼苗体内Fe2+含量与膜脂过氧化产物MDA含量呈极显著的正相关。外源Fe2+、Fe3+、H2O2、Fe2++H2O2、DDTC均能刺激膜脂过氧化作用,而铁离子的螯合剂DTPA则有缓解作用。OH的清除剂苯甲酸钠和甘露醇能明显地抑制渗透胁迫下Fe2+催化的膜脂过氧化作用。这都表明渗透胁迫下水稻幼苗体内铁诱导的膜脂过氧化作用主要是由于其催化Fenton型Haber-Weiss反应形成OH所致。 相似文献