title: Functional analysis of the magnetosome island in Magnetospirillum gryphiswaldense: the mamAB operon is sufficient for magnetite biomineralization.
abstract: Bacterial magnetosomes are membrane-enveloped, nanometer-sized crystals of magnetite, which serve for magnetotactic navigation. All genes implicated in the synthesis of these organelles are located in a conserved genomic magnetosome island (MAI). We performed a comprehensive bioinformatic, proteomic and genetic analysis of the MAI in Magnetospirillum gryphiswaldense. By the construction of large deletion mutants we demonstrate that the entire region is dispensable for growth, and the majority of MAI genes have no detectable function in magnetosome formation and could be eliminated without any effect. Only <25% of the region comprising four major operons could be associated with magnetite biomineralization, which correlated with high expression of these genes and their conservation among magnetotactic bacteria. Whereas only deletion of the mamAB operon resulted in the complete loss of magnetic particles, deletion of the conserved mms6, mamGFDC, and mamXY operons led to severe defects in morphology, size and organization of magnetite crystals. However, strains in which these operons were eliminated together retained the ability to synthesize small irregular crystallites, and weakly aligned in magnetic fields. This demonstrates that whereas the mamGFDC, mms6 and mamXY operons have crucial and partially overlapping functions for the formation of functional magnetosomes, the mamAB operon is the only region of the MAI, which is necessary and sufficient for magnetite biomineralization. Our data further reduce the known minimal gene set required for magnetosome formation and will be useful for future genome engineering approaches.
authors: Department Biologie I, Bereich Mikrobiologie, Ludwig-Maximilians-Universität München, LMU Biozentrum, Planegg-Martinsried, Germany.
authors: Anna
authors: A
authors: Lohsse
authors: Susanne
authors: S
authors: Ullrich
authors: Emanuel
authors: E
authors: Katzmann
authors: Sarah
authors: S
authors: Borg
authors: Gerd
authors: G
authors: Wanner
authors: Michael
authors: M
authors: Richter
authors: Birgit
authors: B
authors: Voigt
authors: Thomas
authors: T
authors: Schweder
authors: Dirk
authors: D
authors: Schüler
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics; D019295:Computational Biology; D052203:Ferrosoferric Oxide / Q000378:metabolism*; D020869:Gene Expression Profiling; D055944:Magnetosomes / Q000737:chemistry / Q000235:genetics*; D042201:Magnetospirillum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009876:Operon / Q000502:physiology*; D015388:Organelles / Q000737:chemistry / Q000235:genetics; D040901:Proteomics
chemical_list: D001426:Bacterial Proteins; D052203:Ferrosoferric Oxide