Plasmid-Encoded Iron Uptake Systems
- Authors: Manuela Di Lorenzo1, Michiel Stork2
- Editors: Marcelo Tolmasky3, Juan Carlos Alonso4
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VIEW AFFILIATIONS HIDE AFFILIATIONSAffiliations: 1: Netherlands Institute of Ecology (NIOO-KNAW), Department of Microbial Ecology, 6708 PB Wageningen, The Netherlands; 2: Institute for Translational Vaccinology, Process Development, 3720 AL Bilthoven, The Netherlands; 3: California State University, Fullerton, CA; 4: Centro Nacional de Biotecnología, Cantoblanco, Madrid, Spain
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Received 30 September 2014 Accepted 01 October 2014 Published 05 December 2014
- Correspondence: Manuela Di Lorenzo, [email protected]

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Abstract:
Plasmids confer genetic information that benefits the bacterial cells containing them. In pathogenic bacteria, plasmids often harbor virulence determinants that enhance the pathogenicity of the bacterium. The ability to acquire iron in environments where it is limited, for instance the eukaryotic host, is a critical factor for bacterial growth. To acquire iron, bacteria have evolved specific iron uptake mechanisms. These systems are often chromosomally encoded, while those that are plasmid-encoded are rare. Two main plasmid types, ColV and pJM1, have been shown to harbor determinants that increase virulence by providing the cell with essential iron for growth. It is clear that these two plasmid groups evolved independently from each other since they do not share similarities either in the plasmid backbones or in the iron uptake systems they harbor. The siderophores aerobactin and salmochelin that are found on ColV plasmids fall in the hydroxamate and catechol group, respectively, whereas both functional groups are present in the anguibactin siderophore, the only iron uptake system found on pJM1-type plasmids. Besides siderophore-mediated iron uptake, ColV plasmids carry additional genes involved in iron metabolism. These systems include ABC transporters, hemolysins, and a hemoglobin protease. ColV- and pJM1-like plasmids have been shown to confer virulence to their bacterial host, and this trait can be completely ascribed to their encoded iron uptake systems.
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Citation: Di Lorenzo M, Stork M. 2014. Plasmid-Encoded Iron Uptake Systems. Microbiol Spectrum 2(6):PLAS-0030-2014. doi:10.1128/microbiolspec.PLAS-0030-2014.




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Abstract:
Plasmids confer genetic information that benefits the bacterial cells containing them. In pathogenic bacteria, plasmids often harbor virulence determinants that enhance the pathogenicity of the bacterium. The ability to acquire iron in environments where it is limited, for instance the eukaryotic host, is a critical factor for bacterial growth. To acquire iron, bacteria have evolved specific iron uptake mechanisms. These systems are often chromosomally encoded, while those that are plasmid-encoded are rare. Two main plasmid types, ColV and pJM1, have been shown to harbor determinants that increase virulence by providing the cell with essential iron for growth. It is clear that these two plasmid groups evolved independently from each other since they do not share similarities either in the plasmid backbones or in the iron uptake systems they harbor. The siderophores aerobactin and salmochelin that are found on ColV plasmids fall in the hydroxamate and catechol group, respectively, whereas both functional groups are present in the anguibactin siderophore, the only iron uptake system found on pJM1-type plasmids. Besides siderophore-mediated iron uptake, ColV plasmids carry additional genes involved in iron metabolism. These systems include ABC transporters, hemolysins, and a hemoglobin protease. ColV- and pJM1-like plasmids have been shown to confer virulence to their bacterial host, and this trait can be completely ascribed to their encoded iron uptake systems.

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Figures

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FIGURE 1a
Schematic representation of a ColV plasmid ( 30 ) showing all open reading frames related to iron uptake, their function, and their membrane localization when relevant. Each system is color-coded. The tra region is shown as a gray box, and the origins of replication are shown as black boxes. Structures of the two siderophores aerobactin and salmochelin S4 are shown within the plasmid.

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FIGURE 1b
Schematic representation of a ColV plasmid ( 30 ) showing all open reading frames related to iron uptake, their function, and their membrane localization when relevant. Each system is color-coded. The tra region is shown as a gray box, and the origins of replication are shown as black boxes. Structures of the two siderophores aerobactin and salmochelin S4 are shown within the plasmid.

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FIGURE 2
Schematic representation of the pJM1 plasmid showing all open reading frames, the structure of anguibactin, and the transport proteins in the membranes. Genes that are involved in siderophore synthesis are shown in red; those involved in transport are blue. Black boxes indicate the location of the antisense RNAs. The shaded proteins in transport are chromosomally encoded. Location of the origins of replication is indicated by a black line.
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