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 The Acidic Repetitive Domain of the Magnetospirillum gryphiswaldense MamJ Protein Displays Hypervariability but Is Not Required for Magnetosome Chain Assembly

2007 ◽  
Vol 189 (17) ◽  
pp. 6437-6446 ◽  
Author(s):  
André Scheffel ◽  
Dirk Schüler
Keyword(s):  
Electron Tomography ◽  
Direct Interaction ◽  
Magnetotactic Bacteria ◽  
Central Domain ◽  
Magnetospirillum Gryphiswaldense ◽  
Binding Domains ◽  
Cytoskeletal Filament ◽  
Distinct Sequence ◽  
Specific Proteins ◽  
Two Hybrid

ABSTRACT Magnetotactic bacteria navigate along the earth's magnetic field using chains of magnetosomes, which are intracellular organelles comprising membrane-enclosed magnetite crystals. The assembly of highly ordered magnetosome chains is under genetic control and involves several specific proteins. Based on genetic and cryo-electron tomography studies, a model was recently proposed in which the acidic MamJ magnetosome protein attaches magnetosome vesicles to the actin-like cytoskeletal filament formed by MamK, thereby preventing magnetosome chains from collapsing. However, the exact functions as well as the mode of interaction between MamK and MamJ are unknown. Here, we demonstrate that several functional MamJ variants from Magnetospirillum gryphiswaldense and other magnetotactic bacteria share an acidic and repetitive central domain, which displays an unusual intra- and interspecies sequence polymorphism, probably caused by homologous recombination between identical copies of Glu- and Pro-rich repeats. Surprisingly, mamJ mutant alleles in which the central domain was deleted retained their potential to restore chain formation in a ΔmamJ mutant, suggesting that the acidic domain is not essential for MamJ's function. Results of two-hybrid experiments indicate that MamJ physically interacts with MamK, and two distinct sequence regions within MamJ were shown to be involved in binding to MamK. Mutant variants of MamJ lacking either of the binding domains were unable to functionally complement the ΔmamJ mutant. In addition, two-hybrid experiments suggest both MamK-binding domains of MamJ confer oligomerization of MamJ. In summary, our data reveal domains required for the functions of the MamJ protein in chain assembly and maintenance and provide the first experimental indications for a direct interaction between MamJ and the cytoskeletal filament protein MamK.

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 Deletion of a fur-Like Gene Affects Iron Homeostasis and Magnetosome Formation in Magnetospirillum gryphiswaldense

2010 ◽  
Vol 192 (16) ◽  
pp. 4192-4204 ◽  
Author(s):  
René Uebe ◽  
Birgit Voigt ◽  
Thomas Schweder ◽  
Dirk Albrecht ◽  
Emanuel Katzmann ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Iron Homeostasis ◽  
Wild Type ◽  
Intracellular Iron ◽  
Magnetospirillum Gryphiswaldense ◽  
Cellular Iron ◽  
Iron Supply ◽  
Iron Requirement ◽  
Magnetite Biomineralization ◽  
Titration Assay

ABSTRACT Magnetotactic bacteria synthesize specific organelles, the magnetosomes, which are membrane-enveloped crystals of the magnetic mineral magnetite (Fe3O4). The biomineralization of magnetite involves the uptake and intracellular accumulation of large amounts of iron. However, it is not clear how iron uptake and biomineralization are regulated and balanced with the biochemical iron requirement and intracellular homeostasis. In this study, we identified and analyzed a homologue of the ferric uptake regulator Fur in Magnetospirillum gryphiswaldense, which was able to complement a fur mutant of Escherichia coli. A fur deletion mutant of M. gryphiswaldense biomineralized fewer and slightly smaller magnetite crystals than did the wild type. Although the total cellular iron accumulation of the mutant was decreased due to reduced magnetite biomineralization, it exhibited an increased level of free intracellular iron, which was bound mostly to a ferritin-like metabolite that was found significantly increased in Mössbauer spectra of the mutant. Compared to that of the wild type, growth of the fur mutant was impaired in the presence of paraquat and under aerobic conditions. Using a Fur titration assay and proteomic analysis, we identified constituents of the Fur regulon. Whereas the expression of most known magnetosome genes was unaffected in the fur mutant, we identified 14 proteins whose expression was altered between the mutant and the wild type, including five proteins whose genes constitute putative iron uptake systems. Our data demonstrate that Fur is a regulator involved in global iron homeostasis, which also affects magnetite biomineralization, probably by balancing the competing demands for biochemical iron supply and magnetite biomineralization.

scholarly journals Fusion expression of nanobodies specific for the insecticide fipronil on magnetosomes in Magnetospirillum gryphiswaldense MSR-1

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Sha Wu ◽  
Fengfei Ma ◽  
Jinxin He ◽  
Qing X. Li ◽  
Bruce D. Hammock ◽  
...  
Keyword(s):  
Colloidal Stability ◽  
Reduced Glutathione ◽  
Magnetotactic Bacteria ◽  
Water Soluble ◽  
Enzyme Linked Immunosorbent Assay ◽  
Crystallographic Structure ◽  
Wild Type ◽  
Magnetospirillum Gryphiswaldense ◽  
Thermal Stable

Abstract Background Magnetic nanoparticles such as magnetosomes modified with antibodies allow a high probability of their interaction with targets of interest. Magnetosomes biomineralized by magnetotactic bacteria are in homogeneous nanoscale size and have crystallographic structure, and high thermal and colloidal stability. Camelidae derived nanobodies (Nbs) are small in size, thermal stable, highly water soluble, easy to produce, and fusible with magnetosomes. We aimed to functionalize Nb-magnetosomes for the analysis of the insecticide fipronil. Results Three recombinant magnetotactic bacteria (CF, CF+ , and CFFF) biomineralizing magnetosomes with different abundance of Nbs displayed on the surface were constructed. Compared to magnetosomes from the wild type Magnetospirillum gryphiswaldense MSR-1, all of the Nb-magnetosomes biosynthesized by strains CF, CF+ , and CFFF showed a detectable level of binding capability to fipronil-horseradish peroxidase (H2-HRP), but none of them recognized free fipronil. The Nb-magnetosomes from CFFF were oxidized with H2O2 or a glutathione mixture consisting of reduced glutathione and oxidized glutathione in vitro and their binding affinity to H2-HRP was decreased, whereas that to free fipronil was enhanced. The magnetosomes treated with the glutathione mixture were employed to develop an enzyme-linked immunosorbent assay for the detection of fipronil in water samples, with average recoveries in a range of 78–101%. Conclusions The economical and environmental-friendly Nb-magnetosomes biomineralized by the bacterial strain MSR-1 can be potentially applied to nanobody-based immunoassays for the detection of fipronil or nanobody-based assays in general.

scholarly journals The Drosophila engrailed and invected Genes: Partners in Regulation, Expression and Function

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 893-906 ◽  
Author(s):  
Elizabeth Gustavson ◽  
Andrew S Goldsborough ◽  
Zehra Ali ◽  
Thomas B Kornberg
Keyword(s):  
Expression Pattern ◽  
Cultured Cells ◽  
Regulatory Region ◽  
Embryonic Lethality ◽  
Wild Type ◽  
Terminal Portion ◽  
Coding Sequence ◽  
Differential Effects ◽  
And Function ◽  
Redundant Functions

Abstract We isolated and characterized numerous engrailed and invected alleles. Among the deficiencies we isolated, a mutant lacking invected sequences was viable and phenotypically normal, a mutant lacking engrailed was an embryo lethal and had slight segmentation defects, and a mutant lacking both engrailed and invected was most severely affected. In seven engrailed alleles, mutations caused translation to terminate prematurely in the central or C-terminal portion of the coding sequence, resulting in embryonic lethality and segmentation defects. Both engrailed and invected expression declined prematurely in these mutant embryos. In wild-type embryos, engrailed and invected are juxtaposed and are expressed in essentially identical patterns. A breakpoint mutant that separates the mgrailed and invected transcription units parceled different aspects of the expression pattern to engrailed or invected. We also found that both genes cause similar defects when expressed ectopically and that the protein products of both genes act to repress transcription in cultured cells. We propose that the varied phenotypes of the engrailed alleles can be explained by the differential effects these mutants have on the combination of engrailed and invected activities, that engrailed and invected share a regulatory region, and that they encode redundant functions.

scholarly journals Multifunktionale bakterielle Nanomagnete für Biotechnologie und Medizin

BIOspektrum ◽  
2021 ◽  
Vol 27 (4) ◽  
pp. 442-444
Author(s):  
Frank Mickoleit ◽  
Sabine Rosenfeldt ◽  
Anna S. Schenk ◽  
Dirk Schüler ◽  
René Uebe
Keyword(s):  
Particle Production ◽  
Magnetotactic Bacteria ◽  
Magnetic Core ◽  
High Yield ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Magnetospirillum Gryphiswaldense ◽  
Core Shell Nanoparticles ◽  
Genetic Toolkit ◽  
The Way

AbstractBacterial magnetosomes represent magnetic core-shell nanoparticles biomineralized by magnetotactic bacteria like Magnetospirillum gryphiswaldense. The establishment of fermentation regimes for high-yield particle production, standardized isolation procedures as well as the development of a genetic toolkit for the generation of “tailored” particles might soon pave the way for the application of engineered magnetosomes in the biomedical and biotechnological field.

scholarly journals Envelope Proteins of the CsmB/CsmF and CsmC/CsmD Motif Families Influence the Size, Shape, and Composition of Chlorosomes in Chlorobaculum tepidum

2009 ◽  
Vol 191 (22) ◽  
pp. 7109-7120 ◽  
Author(s):  
Hui Li ◽  
Donald A. Bryant
Keyword(s):  
Size Composition ◽  
Envelope Proteins ◽  
Structural Motif ◽  
Supramolecular Organization ◽  
Wild Type ◽  
Absorbance Maximum ◽  
Chlorobaculum Tepidum ◽  
Mutant Strains ◽  
Redundant Functions ◽  
Mutational Study

ABSTRACT The chlorosome envelope of Chlorobaculum tepidum contains 10 proteins that belong to four structural motif families. A previous mutational study (N.-U. Frigaard, H. Li, K. J. Milks, and D. A. Bryant, J. Bacteriol. 186:646-653, 2004) suggested that some of these proteins might have redundant functions. Six multilocus mutants were constructed to test the effects of eliminating the proteins of the CsmC/CsmD and CsmB/CsmF motif families, and the resulting strains were characterized physiologically and biochemically. Mutants lacking all proteins of either motif family still assembled functional chlorosomes, and as measured by growth rates of the mutant strains, light harvesting was affected only at the lowest light intensities tested (9 and 32 μmol photons m−2 s−1). The size, composition, and biogenesis of the mutant chlorosomes differed from those of wild-type chlorosomes. Mutants lacking proteins of the CsmC/CsmD motif family produced smaller chlorosomes than did the wild type, and the Qy absorbance maximum for the bacteriochlorophyll c aggregates in these chlorosomes was strongly blueshifted. Conversely, the chlorosomes of mutants lacking proteins of the CsmB/CsmF motif family were larger than wild-type chlorosomes, and the Qy absorption for their bacteriochlorophyll c aggregates was redshifted. When CsmH was eliminated in addition to other proteins of either motif family, chlorosomes had smaller diameters. These data show that the chlorosome envelope proteins of the CsmB/CsmF and CsmC/CsmD families play important roles in determining chlorosome size as well as the assembly and supramolecular organization of the bacteriochlorophyll c aggregates within the chlorosome.

scholarly journals Probing the stability and magnetic properties of magnetosome chains in freeze-dried magnetotactic bacteria

2020 ◽  
Vol 2 (3) ◽  
pp. 1115-1121
Author(s):  
Philipp Bender ◽  
Lourdes Marcano ◽  
Iñaki Orue ◽  
Diego Alba Venero ◽  
Dirk Honecker ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetite Nanoparticles ◽  
Magnetotactic Bacteria ◽  
Magnetic Compass ◽  
High Quality ◽  
Magnetospirillum Gryphiswaldense ◽  
Freeze Dried ◽  
A Chain ◽  
The Stability

Magnetospirillum gryphiswaldense biosynthesize high quality magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass.

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