Iron Oxidation by a Fused Cytochrome-Porin Common to Diverse Iron-Oxidizing Bacteria

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Author(s)Keffer, Jessica L.
Author(s)McAllister, Sean M.
Author(s)Garber, Arkadiy I.
Author(s)Hallahan, Beverly J.
Author(s)Sutherland, Molly C.
Author(s)Rozovsky, Sharon
Author(s)Chan, Clara S.
Date Accessioned2021-12-22T21:02:11Z
Date Available2021-12-22T21:02:11Z
Publication Date2021-07-27
DescriptionThis article was originally published in mBio. The version of record is available at: https://doi.org/10.1128/mBio.01074-21en_US
AbstractIron (Fe) oxidation is one of Earth’s major biogeochemical processes, key to weathering, soil formation, water quality, and corrosion. However, our understanding of microbial contribution is limited by incomplete knowledge of microbial iron oxidation mechanisms, particularly in neutrophilic iron oxidizers. The genomes of many diverse iron oxidizers encode a homolog to an outer membrane cytochrome (Cyc2) shown to oxidize iron in two acidophiles. Phylogenetic analyses show Cyc2 sequences from neutrophiles cluster together, suggesting a common function, though this function has not been verified in these organisms. Therefore, we investigated the iron oxidase function of heterologously expressed Cyc2 from a neutrophilic iron oxidizer Mariprofundus ferrooxydans PV-1. Cyc2PV-1 is capable of oxidizing iron, and its redox potential is 208 ± 20 mV, consistent with the ability to accept electrons from Fe2+ at neutral pH. These results support the hypothesis that Cyc2 functions as an iron oxidase in neutrophilic iron-oxidizing organisms. The results of sequence analysis and modeling reveal that the entire Cyc2 family shares a unique fused cytochrome-porin structure, with a defining consensus motif in the cytochrome region. On the basis of results from structural analyses, we predict that the monoheme cytochrome Cyc2 specifically oxidizes dissolved Fe2+, in contrast to multiheme iron oxidases, which may oxidize solid Fe(II). With our results, there is now functional validation for diverse representatives of Cyc2 sequences. We present a comprehensive Cyc2 phylogenetic tree and offer a roadmap for identifying cyc2/Cyc2 homologs and interpreting their function. The occurrence of cyc2 in many genomes beyond known iron oxidizers presents the possibility that microbial iron oxidation may be a widespread metabolism.en_US
SponsorThis research was funded by the National Science Foundation (EAR-1151682 and BIO-1817651) and the Office of Naval Research (N00014-17-1-2640). We thank the Delaware Biotechnology Institute (DBI) for core instrumentation. Support from the University of Delaware (UD) Center for Bioinformatics & Computational Biology (CBCB) Bioinformatics Core Facility and use of the BIOMIX computer cluster was made possible through funding from Delaware INBRE (NIH NIGMS P20 GM103446), the State of Delaware, and the Delaware Biotechnology Institute.en_US
CitationKeffer JL, McAllister SM, Garber AI, Hallahan BJ, Sutherland MC, Rozovsky S, Chan CS. 2021. Iron oxidation by a fused cytochrome-porin common to diverse iron-oxidizing bacteria. mBio 12:e01074-21. https://doi.org/10.1128/mBio.01074-21en_US
ISSN2150-7511
URLhttps://udspace.udel.edu/handle/19716/29915
Languageen_USen_US
PublishermBioen_US
Keywordscytochromesen_US
Keywordsenvironmental microbiologyen_US
Keywordsiron metabolismen_US
Keywordsiron oxidizersen_US
Keywordsouter membrane proteinsen_US
TitleIron Oxidation by a Fused Cytochrome-Porin Common to Diverse Iron-Oxidizing Bacteriaen_US
TypeArticleen_US
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