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1. Petrobactin, a siderophore produced by Alteromonas , mediates community iron acquisition in the global ocean

   https://doi.org/10.1038/s41396-021-01065-y  

   Manck, Lauren E. ; Park, Jiwoon ; Tully, Benjamin J. ; Poire, Alfonso M. ; Bundy, Randelle M. ; Dupont, Christopher L. ; Barbeau, Katherine A. ( August 2021 , The ISME Journal)

   It is now widely accepted that siderophores play a role in marine iron biogeochemical cycling. However, the mechanisms by which siderophores affect the availability of iron from specific sources and the resulting significance of these processes on iron biogeochemical cycling as a whole have remained largely untested. In this study, we develop a model system for testing the effects of siderophore production on iron bioavailability using the marine copiotroph Alteromonas macleodii ATCC 27126. Through the generation of the knockout cell line ΔasbB::kmr, which lacks siderophore biosynthetic capabilities, we demonstrate that the production of the siderophore petrobactin enables the acquisition of iron from mineral sources and weaker iron-ligand complexes. Notably, the utilization of lithogenic iron, such as that from atmospheric dust, indicates a significant role for siderophores in the incorporation of new iron into marine systems. We have also detected petrobactin, a photoreactive siderophore, directly from seawater in the mid-latitudes of the North Pacific and have identified the biosynthetic pathway for petrobactin in bacterial metagenome-assembled genomes widely distributed across the global ocean. Together, these results improve our mechanistic understanding of the role of siderophore production in iron biogeochemical cycling in the marine environment wherein iron speciation, bioavailability, and residence time can be directly influenced by microbial activities.

    

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2. Ferroportin 3 is a dual‐targeted mitochondrial/chloroplast iron exporter necessary for iron homeostasis in Arabidopsis

   https://doi.org/10.1111/tpj.15286  

   Kim, Leah J. ; Tsuyuki, Kaitlyn M. ; Hu, Fengling ; Park, Emily Y. ; Zhang, Jingwen ; Iraheta, Jennifer G. ; Chia, Ju‐Chen ; Huang, Rong ; Tucker, Avery E. ; Clyne, Madeline ; et al ( June 2021 , The Plant Journal)

   Mitochondria and chloroplasts are organelles with high iron demand that are particularly susceptible to iron‐induced oxidative stress. Despite the necessity of strict iron regulation in these organelles, much remains unknown about mitochondrial and chloroplast iron transport in plants. Here, we propose that Arabidopsis ferroportin 3 (FPN3) is an iron exporter that is dual‐targeted to mitochondria and chloroplasts.FPN3is expressed in shoots, regardless of iron conditions, but its transcripts accumulate under iron deficiency in roots.fpn3mutants cannot grow as well as the wild type under iron‐deficient conditions and their shoot iron levels are lower compared with the wild type. Analyses of iron homeostasis gene expression infpn3mutants and inductively coupled plasma mass spectrometry (ICP‐MS) measurements show that iron levels in the mitochondria and chloroplasts are increased relative to the wild type, consistent with the proposed role of FPN3 as a mitochondrial/plastid iron exporter. In iron‐deficientfpn3mutants, abnormal mitochondrial ultrastructure was observed, whereas chloroplast ultrastructure was not affected, implying that FPN3 plays a critical role in the mitochondria. Overall, our study suggests that FPN3 is essential for optimal iron homeostasis.

    

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3. Syntheses and applications of iron-based functional materials for bioenergy production: a review

   https://doi.org/10.1007/s13399-023-05138-0  

   Li, Xin ; Wang, Lijun ; Shahbazi, Abolghasem ( December 2023 , Biomass Conversion and Biorefinery)

   The earth abundant and environmentally friendly element iron (Fe) forms various functional materials of metallic iron, iron oxides, iron carbides, natural iron ore, and iron-based metallic-organic frameworks. The Fe-based materials have been intensively studied as oxygen carriers, catalysts, adsorbents, and additives in bioenergy production. This review was to provide a fundamental understanding of the syntheses and characteristics of various Fe-based materials for further enhancing their functionalities and facilitating their applications in various bioenergy conversion processes. The syntheses, characteristics, and applications of various iron-based materials for bioenergy conversion published in peer-reviewed articles were first reviewed. The challenges and perspectives of the wide applications of those functional materials in bioenergy conversion were then discussed. The functionalities, stability, and reactivity of Fe-based materials depend on their structures and redox phases. Furthermore, the phase and composition of iron compounds change in a process. More research is needed to analyze the complex phase and composition changes during their applications, and study the type of iron precursors, synthesizing conditions, and the use of promoters and supports to improve their performance in bioenergy conversion. More studies are also needed to develop multifunctional Fe-based materials to be used for multi-duties in a biorefinery and develop green processes to biologically, economically, and sustainably produce those functional materials at a large scale.

    

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4. Iron mobilization during lactation reduces oxygen stores in a diving mammal

   https://doi.org/10.1038/s41467-022-31863-7  

   Shero, Michelle R. ; Kirkham, Amy L. ; Costa, Daniel P. ; Burns, Jennifer M. ( August 2022 , Nature Communications)

   The profound impacts that maternal provisioning of finite energy resources has on offspring survival have been extensively studied across mammals. This study shows that in addition to calories, high hemoprotein concentrations in diving mammals necessitates exceptional female-to-pup iron transfer. Numerous indices of iron mobilization (ferritin, serum iron, total-iron-binding-capacity, transferrin saturation) were significantly elevated during lactation in adult female Weddell seals (Leptonychotes weddellii), but not in skip-breeders. Iron was mobilized from endogenous stores for incorporation into the Weddell seal’s milk at concentrations up to 100× higher than terrestrial mammals. Such high rates of iron offload to offspring drew from the female’s own heme stores and led to compromised physiologic dive capacities (hemoglobin, myoglobin, and total body oxygen stores) after weaning their pups, which was further reflected in shorter dive durations. We demonstrate that lactational iron transfer shapes physiologic dive thresholds, identifying a cost of reproduction to a marine mammal.

    

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5. Comparative proteomics of a versatile, marine, iron‐oxidizing chemolithoautotroph

   https://doi.org/10.1111/1462-2920.16632  

   Barco, Roman_A ; Merino, N. ; Lam, B. ; Budnik, B. ; Kaplan, M. ; Wu, F. ; Amend, J_P ; Nealson, K_H ; Emerson, D. ( June 2024 , Environmental Microbiology)

   This study conducted a comparative proteomic analysis to identify potential genetic markers for the biological function of chemolithoautotrophic iron oxidation in the marine bacteriumGhiorsea bivora. To date, this is the only characterized species in the classZetaproteobacteriathat is not an obligate iron‐oxidizer, providing a unique opportunity to investigate differential protein expression to identify key genes involved in iron‐oxidation at circumneutral pH. Over 1000 proteins were identified under both iron‐ and hydrogen‐oxidizing conditions, with differentially expressed proteins found in both treatments. Notably, a gene cluster upregulated during iron oxidation was identified. This cluster contains genes encoding for cytochromes that share sequence similarity with the known iron‐oxidase, Cyc2. Interestingly, these cytochromes, conserved in both Bacteria and Archaea, do not exhibit the typical β‐barrel structure of Cyc2. This cluster potentially encodes a biological nanowire‐like transmembrane complex containing multiple redox proteins spanning the inner membrane, periplasm, outer membrane, and extracellular space. The upregulation of key genes associated with this complex during iron‐oxidizing conditions was confirmed by quantitative reverse transcription‐PCR. These findings were further supported by electromicrobiological methods, which demonstrated negative current production byG. bivorain a three‐electrode system poised at a cathodic potential. This research provides significant insights into the biological function of chemolithoautotrophic iron oxidation.

    

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