scholarly journals Iron phosphate mediated magnetite synthesis: a bioinspired approach

2021 ◽  
Author(s):  
Giulia Mirabello ◽  
Matthew GoodSmith ◽  
Paul H. H. Bomans ◽  
Linus Stegbauer ◽  
Derk Joester ◽  
...  
Keyword(s):  
Magnetotactic Bacteria ◽  
Iron Phosphate ◽  
Magnetite Biomineralization ◽  
Active Investigation

The biomineralization of intracellular magnetite in magnetotactic bacteria (MTB) is an area of active investigation. Previous work has provided evidence that magnetite biomineralization begins with the formation of an amorphous...

scholarly journals A Compass To Boost Navigation: Cell Biology of Bacterial Magnetotaxis

2020 ◽  
Vol 202 (21) ◽  
Author(s):  
Frank D. Müller ◽  
Dirk Schüler ◽  
Daniel Pfeiffer
Keyword(s):  
Magnetic Field ◽  
Cell Biology ◽  
Molecular Mechanisms ◽  
Magnetotactic Bacteria ◽  
Genetically Engineered ◽  
Model Organisms ◽  
Complex Cell ◽  
Magnetite Biomineralization ◽  
Directed Motility ◽  
The Impact

ABSTRACT Magnetotactic bacteria are aquatic or sediment-dwelling microorganisms able to take advantage of the Earth’s magnetic field for directed motility. The source of this amazing trait is magnetosomes, unique organelles used to synthesize single nanometer-sized crystals of magnetic iron minerals that are queued up to build an intracellular compass. Most of these microorganisms cannot be cultivated under controlled conditions, much less genetically engineered, with only few exceptions. However, two of the genetically amenable Magnetospirillum species have emerged as tractable model organisms to study magnetosome formation and magnetotaxis. Recently, much has been revealed about the process of magnetosome biogenesis and dedicated structures for magnetosome dynamics and positioning, which suggest an unexpected cellular intricacy of these organisms. In this minireview, we summarize new insights and place the molecular mechanisms of magnetosome formation in the context of the complex cell biology of Magnetospirillum spp. First, we provide an overview on magnetosome vesicle synthesis and magnetite biomineralization, followed by a discussion of the perceptions of dynamic organelle positioning and its biological implications, which highlight that magnetotactic bacteria have evolved sophisticated mechanisms to construct, incorporate, and inherit a unique navigational device. Finally, we discuss the impact of magnetotaxis on motility and its interconnection with chemotaxis, showing that magnetotactic bacteria are outstandingly adapted to lifestyle and habitat.

scholarly journals A Large Gene Cluster Encoding Several Magnetosome Proteins Is Conserved in Different Species of Magnetotactic Bacteria

2001 ◽  
Vol 67 (10) ◽  
pp. 4573-4582 ◽  
Author(s):  
Karen Grünberg ◽  
Cathrin Wawer ◽  
Bradley M. Tebo ◽  
Dirk Schüler
Keyword(s):  
Gene Cluster ◽  
Serine Proteases ◽  
Major Gene ◽  
Magnetotactic Bacteria ◽  
Large Gene ◽  
Specific Proteins ◽  
Magnetite Biomineralization ◽  
Cation Diffusion Facilitators ◽  
Tetratricopeptide Repeat Proteins ◽  
Genomic Regions

ABSTRACT In magnetotactic bacteria, a number of specific proteins are associated with the magnetosome membrane (MM) and may have a crucial role in magnetite biomineralization. We have cloned and sequenced the genes of several of these polypeptides in the magnetotactic bacterium Magnetospirillum gryphiswaldense that could be assigned to two different genomic regions. Except for mamA, none of these genes have been previously reported to be related to magnetosome formation. Homologous genes were found in the genome sequences ofM. magnetotacticum and magnetic coccus strain MC-1. The MM proteins identified display homology to tetratricopeptide repeat proteins (MamA), cation diffusion facilitators (MamB), and HtrA-like serine proteases (MamE) or bear no similarity to known proteins (MamC and MamD). A major gene cluster containing several magnetosome genes (including mamA and mamB) was found to be conserved in all three of the strains investigated. ThemamAB cluster also contains additional genes that have no known homologs in any nonmagnetic organism, suggesting a specific role in magnetosome formation.

scholarly journals Bacterioferritin ofMagnetospirillum gryphiswaldenseIs a Heterotetraeicosameric Complex Composed of Functionally Distinct Subunits but Is Not Involved in Magnetite Biomineralization

mBio ◽  
2019 ◽  
Vol 10 (3) ◽  
Author(s):  
René Uebe ◽  
Frederik Ahrens ◽  
Jörg Stang ◽  
Katharina Jäger ◽  
Lars H. Böttger ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Magnetotactic Bacteria ◽  
Functional Differentiation ◽  
Spectroscopic Techniques ◽  
Content Type ◽  
Magnetospirillum Gryphiswaldense ◽  
Ferroxidase Activity ◽  
Magnetite Biomineralization ◽  
Field Lines

ABSTRACTThe biomineralization pathway of magnetite in magnetotactic bacteria is still poorly understood and a matter of intense debates. In particular, the existence, nature, and location of possible mineral precursors of magnetite are not clear. One possible precursor has been suggested to be ferritin-bound ferrihydrite. To clarify its role for magnetite biomineralization, we analyzed and characterized ferritin-like proteins from the magnetotactic alphaproteobacteriumMagnetospirillum gryphiswaldenseMSR-1, employing genetic, biochemical, and spectroscopic techniques. Transmission Mössbauer spectroscopy of the wild type (WT) and a bacterioferritin (bfr) deletion strain uncovered that the presence of ferrihydrite in cells is coupled to the presence of Bfr. However,bfranddpsdeletion mutants, encoding another ferritin-like protein, or even mutants with their codeletion had no impact on magnetite formation in MSR-1. Thus, ferritin-like proteins are not involved in magnetite biomineralization and Bfr-bound ferrihydrite is not a precursor of magnetite biosynthesis. Using transmission electron microscopy and bacterial two-hybrid and electrophoretic methods, we also show that MSR-1 Bfr is an atypical representative of the Bfr subfamily, as it forms tetraeicosameric complexes from two distinct subunits. Furthermore, our analyses revealed that these subunits are functionally divergent, with Bfr1 harboring a ferroxidase activity while only Bfr2 contributes to heme binding. Because of this functional differentiation and the poor formation of homooligomeric Bfr1 complexes, only heterooligomeric Bfr protects cells from oxidative stressin vivo.In summary, our results not only provide novel insights into the biomineralization of magnetite but also reveal the unique properties of so-far-uncharacterized heterooligomeric bacterioferritins.IMPORTANCEMagnetotactic bacteria likeMagnetospirillum gryphiswaldenseare able to orient along magnetic field lines due to the intracellular formation of magnetite nanoparticles. Biomineralization of magnetite has been suggested to require a yet-unknown ferritin-like ferrihydrite component. Here, we report the identification of a bacterioferritin as the source of ferrihydrite inM. gryphiswaldenseand show that, contrary to previous reports, bacterioferritin is not involved in magnetite biomineralization but required for oxidative stress resistance. Additionally, we show that bacterioferritin ofM. gryphiswaldenseis an unusual member of the bacterioferritin subfamily as it is composed of two functionally distinct subunits. Thus, our findings extend our understanding of the bacterioferritin subfamily and also solve a longstanding question about the magnetite biomineralization pathway.

scholarly journals The Major Magnetosome Proteins MamGFDC Are Not Essential for Magnetite Biomineralization in Magnetospirillum gryphiswaldense but Regulate the Size of Magnetosome Crystals

2007 ◽  
Vol 190 (1) ◽  
pp. 377-386 ◽  
Author(s):  
André Scheffel ◽  
Astrid Gärdes ◽  
Karen Grünberg ◽  
Gerhard Wanner ◽  
Dirk Schüler
Keyword(s):  
Magnetotactic Bacteria ◽  
Crystal Formation ◽  
Wild Type ◽  
Unknown Mechanism ◽  
Magnetospirillum Gryphiswaldense ◽  
Type Size ◽  
Specific Proteins ◽  
Magnetite Biomineralization ◽  
Redundant Functions ◽  
Small Hydrophobic

ABSTRACT Magnetospirillum gryphiswaldense and related magnetotactic bacteria form magnetosomes, which are membrane-enclosed organelles containing crystals of magnetite (Fe3O4) that cause the cells to orient in magnetic fields. The characteristic sizes, morphologies, and patterns of alignment of magnetite crystals are controlled by vesicles formed of the magnetosome membrane (MM), which contains a number of specific proteins whose precise roles in magnetosome formation have remained largely elusive. Here, we report on a functional analysis of the small hydrophobic MamGFDC proteins, which altogether account for nearly 35% of all proteins associated with the MM. Although their high levels of abundance and conservation among magnetotactic bacteria had suggested a major role in magnetosome formation, we found that the MamGFDC proteins are not essential for biomineralization, as the deletion of neither mamC, encoding the most abundant magnetosome protein, nor the entire mamGFDC operon abolished the formation of magnetite crystals. However, cells lacking mamGFDC produced crystals that were only 75% of the wild-type size and were less regular than wild-type crystals with respect to morphology and chain-like organization. The inhibition of crystal formation could not be eliminated by increased iron concentrations. The growth of mutant crystals apparently was not spatially constrained by the sizes of MM vesicles, as cells lacking mamGFDC formed vesicles with sizes and shapes nearly identical to those formed by wild-type cells. However, the formation of wild-type-size magnetite crystals could be gradually restored by in-trans complementation with one, two, and three genes of the mamGFDC operon, regardless of the combination, whereas the expression of all four genes resulted in crystals exceeding the wild-type size. Our data suggest that the MamGFDC proteins have partially redundant functions and, in a cumulative manner, control the growth of magnetite crystals by an as-yet-unknown mechanism.

scholarly journals Magnetite biomineralization in Magnetospirillum magneticum is regulated by a switch-like behavior in the HtrA protease MamE

2016 ◽  
Author(s):  
David M. Hershey ◽  
Patrick J. Browne ◽  
Anthony T. Iavarone ◽  
Joan Teyra ◽  
Eun H. Lee ◽  
...  
Keyword(s):  
Magnetic Particles ◽  
Aquatic Organisms ◽  
Magnetotactic Bacteria ◽  
Proteolytic Processing ◽  
Pdz Domains ◽  
Peptide Substrate ◽  
Magnetite Biomineralization ◽  
Magnetospirillum Magneticum

AbstractMagnetotactic bacteria are aquatic organisms that produce subcellular magnetic particles in order to orient in the earth’s geomagnetic field. MamE, a predicted HtrA protease required to produce magnetite crystals in the magnetotactic bacteriumMagnetospirillum magneticumAMB-1, was recently shown to promote the proteolytic processing of itself and two other biomineralization factorsin vivo. Here, we have analyzed thein vivoprocessing patterns of three proteolytic targets and used this information to reconstitute proteolysis with a purified form of MamEin vitro. MamE cleaves a custom peptide substrate with positive cooperativity, and its auto-proteolysis can be stimulated with exogenous substrates or peptides that bind to either of its PDZ domains. A misregulated form of the protease that circumvents specific genetic requirements for proteolysis causes biomineralization defects, showing that proper regulation of its activity is required during magnetite biosynthesisin vivo. Our results represent the first reconstitution of MamE’s proteolytic activity and show that its behavior is consistent with the previously proposed checkpoint model for biomineralization.

scholarly journals Crystal growth of bullet-shaped magnetite in magnetotactic bacteria of the Nitrospirae phylum

2015 ◽  
Vol 12 (103) ◽  
pp. 20141288 ◽  
Author(s):  
Jinhua Li ◽  
Nicolas Menguy ◽  
Christophe Gatel ◽  
Victor Boureau ◽  
Etienne Snoeck ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Protein S ◽  
Magnetotactic Bacteria ◽  
Intracellular Membrane ◽  
The Earth ◽  
Transmission Electron ◽  
Magnetite Biomineralization ◽  
Field Lines ◽  
Multiple Step

Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth's magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB group. We observed a multiple-step crystal growth of MYR-1 magnetite: initial isotropic growth forming cubo-octahedral particles (less than approx. 40 nm), subsequent anisotropic growth and a systematic final elongation along [001] direction. During the crystal growth, one major {111} face is well developed and preserved at the larger basal end of the crystal. The basal {111} face appears to be terminated by a tetrahedral–octahedral-mixed iron surface, suggesting dimensional advantages for binding protein(s), which may template the crystallization of magnetite. This study offers new insights for understanding magnetite biomineralization within the Nitrospirae phylum.

scholarly journals MamO Is a Repurposed Serine Protease that Promotes Magnetite Biomineralization through Direct Transition Metal Binding in Magnetotactic Bacteria

PLoS Biology ◽  
2016 ◽  
Vol 14 (3) ◽  
pp. e1002402 ◽  
Author(s):  
David M. Hershey ◽  
Xuefeng Ren ◽  
Ryan A. Melnyk ◽  
Patrick J. Browne ◽  
Ertan Ozyamak ◽  
...  
Keyword(s):  
Transition Metal ◽  
Serine Protease ◽  
Metal Binding ◽  
Magnetotactic Bacteria ◽  
Direct Transition ◽  
Magnetite Biomineralization

The Scanning Electron Microscopic Observation of the Vestibular Sensory Epithelia

1969 ◽  
Vol 27 ◽  
pp. 40-41
Author(s):  
D.J. Lim ◽  
W.C. Lane
Keyword(s):  
Semicircular Canals ◽  
Electron Microscopic Observation ◽  
Gravitational Acceleration ◽  
Electron Microscopic ◽  
Sensory Epithelia ◽  
Scanning Electron Microscopic ◽  
Vestibular Sensory Epithelia ◽  
And Function ◽  
Sand Piles ◽  
Active Investigation

The morphology and function of the vestibular sensory organs has been extensively studied during the last decade with the advent of electron microscopy and electrophysiology. The opening of the space age also accelerated active investigation in this area, since this organ is responsible for the sensation of balance and of linear, angular and gravitational acceleration.The vestibular sense organs are formed by the saccule, utricle and three ampullae of the semicircular canals. The maculae (sacculi and utriculi) have otolithic membranes on the top of the sensory epithelia. The otolithic membrane is formed by a layer of thick gelatin and sand-piles of calcium carbonate crystals (Fig.l).

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