Distributions of iron, phosphorus and sulfur along trichomes of the cyanobacteria Trichodesmium.

The nonheterocystous cyanobacterium Trichodesmium fixes C and N concurrently during the light period in tropical and subtropical oceans. Synchrotron mapping of Fe, P and S in trichomes of Trichodesmium erythraeum Erhenberg IMS 101 (CCMP 1985) collected during exponential and senescent growth revealed that 16% of trichomes contained sections of up to 25 cells with ca. 2-fold elevated Fe and S but ca.

LOCALIZATION OF IRON WITHIN CENTRIC DIATOMS OF THE GENUS THALASSIOSIRA(1).

The cellular iron (Fe) quota of centric diatoms has been shown to vary in response to the ambient dissolved Fe concentration; however, it is not known how centric diatoms store excess intracellular Fe. Here, we use synchrotron X-ray fluorescence (SXRF) element mapping to identify Fe storage features in cells of Thalassiosira pseudonana Hasle et Heimdal and Thalassiosira weissflogii G. A.

The unique biogeochemical signature of the marine diazotroph trichodesmium.

The elemental composition of phytoplankton can depart from canonical Redfield values under conditions of nutrient limitation or production (e.g., N fixation).

Fe isotope fractionation during equilibration of Fe-organic complexes.

Despite the importance of Fe-organic complexes in the environment, few studies have investigated Fe isotope effects driven by changes in Fe coordination that involve organic ligands. Previous experimental (Dideriksen et al., 2008, Earth Planet Sci.

Characterization of an electron conduit between bacteria and the extracellular environment.

A number of species of Gram-negative bacteria can use insoluble minerals of Fe(III) and Mn(IV) as extracellular respiratory electron acceptors. In some species of Shewanella, deca-heme electron transfer proteins lie at the extracellular face of the outer membrane (OM), where they can interact with insoluble substrates. To reduce extracellular substrates, these redox proteins must be charged by the inner membrane/periplasmic electron transfer system.

Determination of metal speciation by reverse titrations.

A new method is proposed to determine metal speciation by varying the concentration of a competing ligand at a constant metal concentration, with detection by cathodic stripping voltammetry. The free metal ion concentration is gradually lowered from its natural level while the method probes progressively deeper into the already complexed metal fraction: it is therefore a reverse titration rather than the forward titration which is used for conventional complexing ligand titrations. The sensitivity is greatest at the lowest free metal ion concentration, where it matters most, and the method can be carried out in a single sample aliquot in the voltammetric cell.