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Saghaï A, Hallin S. Diversity and ecology of NrfA-dependent ammonifying microorganisms. Trends Microbiol 2024; 32:602-613. [PMID: 38462391 DOI: 10.1016/j.tim.2024.02.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 02/11/2024] [Accepted: 02/13/2024] [Indexed: 03/12/2024]
Abstract
Nitrate ammonifiers are a taxonomically diverse group of microorganisms that reduce nitrate to ammonium, which is released, and thereby contribute to the retention of nitrogen in ecosystems. Despite their importance for understanding the fate of nitrate, they remain a largely overlooked group in the nitrogen cycle. Here, we present the latest advances on free-living microorganisms using NrfA to reduce nitrite during ammonification. We describe their diversity and ecology in terrestrial and aquatic environments, as well as the environmental factors influencing the competition for nitrate with denitrifiers that reduce nitrate to gaseous nitrogen species, including the greenhouse gas nitrous oxide (N2O). We further review the capacity of ammonifiers for other redox reactions, showing that they likely play multiple roles in the cycling of elements.
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Affiliation(s)
- Aurélien Saghaï
- Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Sara Hallin
- Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
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2
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Saghaï A, Pold G, Jones CM, Hallin S. Phyloecology of nitrate ammonifiers and their importance relative to denitrifiers in global terrestrial biomes. Nat Commun 2023; 14:8249. [PMID: 38086813 PMCID: PMC10716430 DOI: 10.1038/s41467-023-44022-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 11/28/2023] [Indexed: 12/18/2023] Open
Abstract
Nitrate ammonification is important for soil nitrogen retention. However, the ecology of ammonifiers and their prevalence compared with denitrifiers, being competitors for nitrate, are overlooked. Here, we screen 1 million genomes for nrfA and onr, encoding ammonifier nitrite reductases. About 40% of ammonifier assemblies carry at least one denitrification gene and show higher potential for nitrous oxide production than consumption. We then use a phylogeny-based approach to recruit gene fragments of nrfA, onr and denitrification nitrite reductase genes (nirK, nirS) in 1861 global terrestrial metagenomes. nrfA outnumbers the nearly negligible onr counts in all biomes, but denitrification genes dominate, except in tundra. Random forest modelling teases apart the influence of the soil C/N on nrfA-ammonifier vs denitrifier abundance, showing an effect of nitrate rather than carbon content. This study demonstrates the multiple roles nitrate ammonifiers play in nitrogen cycling and identifies factors ultimately controlling the fate of soil nitrate.
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Affiliation(s)
- Aurélien Saghaï
- Swedish University of Agricultural Sciences, Department of Forest Mycology and Plant Pathology, Uppsala, Sweden
| | - Grace Pold
- Swedish University of Agricultural Sciences, Department of Forest Mycology and Plant Pathology, Uppsala, Sweden
| | - Christopher M Jones
- Swedish University of Agricultural Sciences, Department of Forest Mycology and Plant Pathology, Uppsala, Sweden
| | - Sara Hallin
- Swedish University of Agricultural Sciences, Department of Forest Mycology and Plant Pathology, Uppsala, Sweden.
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3
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Ilcu L, Denkhaus L, Brausemann A, Zhang L, Einsle O. Architecture of the Heme-translocating CcmABCD/E complex required for Cytochrome c maturation. Nat Commun 2023; 14:5190. [PMID: 37626034 PMCID: PMC10457321 DOI: 10.1038/s41467-023-40881-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023] Open
Abstract
Mono- and multiheme cytochromes c are post-translationally matured by the covalent attachment of heme. For this, Escherichia coli employs the most complex type of maturation machineries, the Ccm-system (for cytochrome c maturation). It consists of two membrane protein complexes, one of which shuttles heme across the membrane to a mobile chaperone that then delivers the cofactor to the second complex, an apoprotein:heme lyase, for covalent attachment. Here we report cryo-electron microscopic structures of the heme translocation complex CcmABCD from E. coli, alone and bound to the heme chaperone CcmE. CcmABCD forms a heterooctameric complex centered around the ABC transporter CcmAB that does not by itself transport heme. Our data suggest that the complex flops a heme group from the inner to the outer leaflet at its CcmBC interfaces, driven by ATP hydrolysis at CcmA. A conserved heme-handling motif (WxWD) at the periplasmic side of CcmC rotates the heme by 90° for covalent attachment to the heme chaperone CcmE that we find interacting exclusively with the CcmB subunit.
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Affiliation(s)
- Lorena Ilcu
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, 79104, Freiburg im Breisgau, Germany
| | - Lukas Denkhaus
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, 79104, Freiburg im Breisgau, Germany
| | - Anton Brausemann
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, 79104, Freiburg im Breisgau, Germany
| | - Lin Zhang
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, 79104, Freiburg im Breisgau, Germany.
| | - Oliver Einsle
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, 79104, Freiburg im Breisgau, Germany.
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4
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Zavarzina DG, Merkel AY, Klyukina AA, Elizarov IM, Pikhtereva VA, Rusakov VS, Chistyakova NI, Ziganshin RH, Maslov AA, Gavrilov SN. Iron or sulfur respiration-an adaptive choice determining the fitness of a natronophilic bacterium Dethiobacter alkaliphilus in geochemically contrasting environments. Front Microbiol 2023; 14:1108245. [PMID: 37520367 PMCID: PMC10376724 DOI: 10.3389/fmicb.2023.1108245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 06/26/2023] [Indexed: 08/01/2023] Open
Abstract
Haloalkaliphilic microorganisms are double extremophiles functioning optimally at high salinity and pH. Their typical habitats are soda lakes, geologically ancient yet widespread ecosystems supposed to harbor relict microbial communities. We compared metabolic features and their determinants in two strains of the natronophilic species Dethiobacter alkaliphilus, the only cultured representative of the class "Dethiobacteria" (Bacillota). The strains of D. alkaliphilus were previously isolated from geographically remote Mongolian and Kenyan soda lakes. The type strain AHT1T was described as a facultative chemolithoautotrophic sulfidogen reducing or disproportionating sulfur or thiosulfate, while strain Z-1002 was isolated as a chemolithoautotrophic iron reducer. Here, we uncovered the iron reducing ability of strain AHT1T and the ability of strain Z-1002 for thiosulfate reduction and anaerobic Fe(II) oxidation. Key catabolic processes sustaining the growth of both D. alkaliphilus strains appeared to fit the geochemical settings of two contrasting natural alkaline environments, sulfur-enriched soda lakes and iron-enriched serpentinites. This hypothesis was supported by a meta-analysis of Dethiobacterial genomes and by the enrichment of a novel phylotype from a subsurface alkaline aquifer under Fe(III)-reducing conditions. Genome analysis revealed multiheme c-type cytochromes to be the most probable determinants of iron and sulfur redox transformations in D. alkaliphilus. Phylogeny reconstruction showed that all the respiratory processes in this organism are likely provided by evolutionarily related early forms of unconventional octaheme tetrathionate and sulfite reductases and their structural analogs, OmhA/OcwA Fe(III)-reductases. Several phylogenetically related determinants of anaerobic Fe(II) oxidation were identified in the Z-1002 genome, and the oxidation process was experimentally demonstrated. Proteomic profiling revealed two distinct sets of multiheme cytochromes upregulated in iron(III)- or thiosulfate-respiring cells and the cytochromes peculiar for Fe(II) oxidizing cells. We suggest that maintaining high variation in multiheme cytochromes is an effective adaptive strategy to occupy geochemically contrasting alkaline environments. We propose that sulfur-enriched soda lakes could be secondary habitats for D. alkaliphilus compared to Fe-rich serpentinites, and that the ongoing evolution of Dethiobacterales could retrace the evolutionary path that may have occurred in prokaryotes at a turning point in the biosphere's history, when the intensification of the sulfur cycle outweighed the global significance of the iron cycle.
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Affiliation(s)
- Daria G. Zavarzina
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Alexander Yu Merkel
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Alexandra A. Klyukina
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Ivan M. Elizarov
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Valeria A. Pikhtereva
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | | | | | - Rustam H. Ziganshin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Alexey A. Maslov
- Faculty of Geology, Lomonosov Moscow State University, Moscow, Russia
| | - Sergey N. Gavrilov
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
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5
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Baquero DP, Cvirkaite-Krupovic V, Hu SS, Fields JL, Liu X, Rensing C, Egelman EH, Krupovic M, Wang F. Extracellular cytochrome nanowires appear to be ubiquitous in prokaryotes. Cell 2023; 186:2853-2864.e8. [PMID: 37290436 PMCID: PMC10330847 DOI: 10.1016/j.cell.2023.05.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/04/2023] [Accepted: 05/10/2023] [Indexed: 06/10/2023]
Abstract
Electrically conductive appendages from the anaerobic bacterium Geobacter sulfurreducens, recently identified as extracellular cytochrome nanowires (ECNs), have received wide attention due to numerous potential applications. However, whether other organisms employ similar ECNs for electron transfer remains unknown. Here, using cryoelectron microscopy, we describe the atomic structures of two ECNs from two major orders of hyperthermophilic archaea present in deep-sea hydrothermal vents and terrestrial hot springs. Homologs of Archaeoglobus veneficus ECN are widespread among mesophilic methane-oxidizing Methanoperedenaceae, alkane-degrading Syntrophoarchaeales archaea, and in the recently described megaplasmids called Borgs. The ECN protein subunits lack similarities in their folds; however, they share a common heme arrangement, suggesting an evolutionarily optimized heme packing for efficient electron transfer. The detection of ECNs in archaea suggests that filaments containing closely stacked hemes may be a common and widespread mechanism for long-range electron transfer in both prokaryotic domains of life.
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Affiliation(s)
- Diana P Baquero
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Archaeal Virology Unit, Paris 75015, France
| | | | - Shengen Shawn Hu
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA
| | - Jessie Lynda Fields
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35233, USA
| | - Xing Liu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Christopher Rensing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA.
| | - Mart Krupovic
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Archaeal Virology Unit, Paris 75015, France.
| | - Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA; Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35233, USA; O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35233, USA.
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6
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Tikhonova TV, Osipov EM, Dergousova NI, Boyko KM, Elizarov IM, Gavrilov SN, Khrenova MG, Robb FT, Solovieva AY, Bonch-Osmolovskaya EA, Popov VO. Extracellular Fe(III) reductase structure reveals a modular organization enabling S-layer insertion and electron transfer to insoluble substrates. Structure 2023; 31:174-184.e3. [PMID: 36630959 DOI: 10.1016/j.str.2022.12.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 10/16/2022] [Accepted: 12/14/2022] [Indexed: 01/12/2023]
Abstract
The thermophilic anaerobic Gram-positive bacterium Carboxydothermus ferrireducens utilizes insoluble Fe(III) oxides as electron acceptors in respiratory processes using an extracellular 11-heme cytochrome c OmhA as a terminal reductase. OmhA is able to transfer electrons to soluble and insoluble Fe(III) compounds, substrates of multiheme oxidoreductases, and soluble electron shuttles. The crystal structure of OmhA at 2.5 Å resolution shows that it consists of two functionally distinct parts: the cytochrome с electron transfer and the S-layer binding domains. Nonaheme C-terminal subdomain of the cytochrome с domain is structurally similar to the extracellular multiheme cytochrome OcwA from the metal-reducing Gram-positive bacterium "Thermincola potens." S-layer binding domain of OmhA is responsible for interaction with the S-layer that surrounds the Carboxydothermus ferrireducens cell envelope. The structural foundations enabling the embedding of extracellular multiheme cytochromes to the S-layer of a Gram-positive-type cell wall and putative electron transfer pathways to insoluble minerals are discussed.
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Affiliation(s)
- Tamara V Tikhonova
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation
| | - Evgenii M Osipov
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation; Biocrystallography, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Herestraat 49, Leuven 3000, Belgium
| | - Natalia I Dergousova
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation
| | - Konstantin M Boyko
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation
| | - Ivan M Elizarov
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation
| | - Sergey N Gavrilov
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation
| | - Maria G Khrenova
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation; Department of Chemistry, Lomonosov Moscow State University, 1 Lenin Hills, Building 3, Moscow 119991, Russian Federation
| | - Frank T Robb
- Institute of Marine and Environmental Technology, Center for Environmental Science, University of Maryland, 701 E. Pratt Street, Baltimore, MD 21202, USA
| | - Anastasia Y Solovieva
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation
| | - Elizaveta A Bonch-Osmolovskaya
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation; Department of Biology, Lomonosov Moscow State University, 1 Lenin Hills, Building 12, Moscow 119991, Russian Federation
| | - Vladimir O Popov
- Research Center of Biotechnology of the Russian Academy of Sciences, 33 Leninsky Prospect, Building 1, Moscow 119071, Russian Federation; Department of Biology, Lomonosov Moscow State University, 1 Lenin Hills, Building 12, Moscow 119991, Russian Federation.
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7
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Zhong F, Albert T, Moënne-Loccoz P, Pletneva EV. Influence of the Interdomain Interface on Structural and Redox Properties of Multiheme Proteins. Inorg Chem 2022; 61:20949-20963. [PMID: 36493379 PMCID: PMC11034829 DOI: 10.1021/acs.inorgchem.2c03427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Multiheme proteins are important in energy conversion and biogeochemical cycles of nitrogen and sulfur. A diheme cytochrome c4 (c4) was used as a model to elucidate roles of the interdomain interface on properties of iron centers in its hemes A and B. Isolated monoheme domains c4-A and c4-B, together with the full-length diheme c4 and its Met-to-His ligand variants, were characterized by a variety of spectroscopic and stability measurements. In both isolated domains, the heme iron is Met/His-ligated at pH 5.0, as in the full-length c4, but becomes His/His-ligated in c4-B at higher pH. Intradomain contacts in c4-A are minimally affected by the separation of c4-A and c4-B domains, and isolated c4-A is folded. In contrast, the isolated c4-B is partially unfolded, and the interface with c4-A guides folding of this domain. The c4-A and c4-B domains have the propensity to interact even without the polypeptide linker. Thermodynamic cycles have revealed properties of monomeric folded isolated domains, suggesting that ferrous (FeII), but not ferric (FeIII) c4-A and c4-B, is stabilized by the interface. This study illustrates the effects of the interface on tuning structural and redox properties of multiheme proteins and enriches our understanding of redox-dependent complexation.
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Affiliation(s)
- Fangfang Zhong
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR 97239, United States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR 97239, United States
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Wang F, Chan CH, Suciu V, Mustafa K, Ammend M, Si D, Hochbaum AI, Egelman EH, Bond DR. Structure of Geobacter OmcZ filaments suggests extracellular cytochrome polymers evolved independently multiple times. eLife 2022; 11:81551. [PMID: 36062910 PMCID: PMC9473688 DOI: 10.7554/elife.81551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 09/03/2022] [Indexed: 11/26/2022] Open
Abstract
While early genetic and low-resolution structural observations suggested that extracellular conductive filaments on metal-reducing organisms such as Geobacter were composed of type IV pili, it has now been established that bacterial c-type cytochromes can polymerize to form extracellular filaments capable of long-range electron transport. Atomic structures exist for two such cytochrome filaments, formed from the hexaheme cytochrome OmcS and the tetraheme cytochrome OmcE. Due to the highly conserved heme packing within the central OmcS and OmcE cores, and shared pattern of heme coordination between subunits, it has been suggested that these polymers have a common origin. We have now used cryo-electron microscopy (cryo-EM) to determine the structure of a third extracellular filament, formed from the Geobacter sulfurreducens octaheme cytochrome, OmcZ. In contrast to the linear heme chains in OmcS and OmcE from the same organism, the packing of hemes, heme:heme angles, and between-subunit heme coordination is quite different in OmcZ. A branched heme arrangement within OmcZ leads to a highly surface exposed heme in every subunit, which may account for the formation of conductive biofilm networks, and explain the higher measured conductivity of OmcZ filaments. This new structural evidence suggests that conductive cytochrome polymers arose independently on more than one occasion from different ancestral multiheme proteins.
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Affiliation(s)
- Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, United States
| | - Chi Ho Chan
- Department of Plant and MIcrobial Biology, University of Minnesota, St. Paul, United States
| | - Victor Suciu
- Division of Computing and Software Systems, University of Washington Bothell, Bothell, United States
| | - Khawla Mustafa
- Department of Chemistry, University of California, Irvine, Irvine, United States
| | - Madeline Ammend
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, United States
| | - Dong Si
- Division of Computing and Software Systems, University of Washington Bothell, Bothell, United States
| | - Allon I Hochbaum
- Department of Chemistry, University of California, Irvine, Irvine, United States
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, United States
| | - Daniel R Bond
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, United States
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