1
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Awal RP, Müller FD, Pfeiffer D, Monteil CL, Perrière G, Lefèvre CT, Schüler D. Experimental analysis of diverse actin-like proteins from various magnetotactic bacteria by functional expression in Magnetospirillum gryphiswaldense. mBio 2023; 14:e0164923. [PMID: 37823629 PMCID: PMC10653835 DOI: 10.1128/mbio.01649-23] [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: 06/28/2023] [Accepted: 08/29/2023] [Indexed: 10/13/2023] Open
Abstract
IMPORTANCE To efficiently navigate within the geomagnetic field, magnetotactic bacteria (MTB) align their magnetosome organelles into chains, which are organized by the actin-like MamK protein. Although MamK is the most highly conserved magnetosome protein common to all MTB, its analysis has been confined to a small subgroup owing to the inaccessibility of most MTB. Our study takes advantage of a genetically tractable host where expression of diverse MamK orthologs together with a resurrected MamK LUCA and uncharacterized actin-like Mad28 proteins from deep-branching MTB resulted in gradual restoration of magnetosome chains in various mutants. Our results further indicate the existence of species-specific MamK interactors and shed light on the evolutionary relationships of one of the key proteins associated with bacterial magnetotaxis.
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Affiliation(s)
- Ram Prasad Awal
- Department of Microbiology, Universitat Bayreuth, Bayreuth, Germany
| | - Frank D. Müller
- Department of Microbiology, Universitat Bayreuth, Bayreuth, Germany
| | - Daniel Pfeiffer
- Department of Microbiology, Universitat Bayreuth, Bayreuth, Germany
| | - Caroline L. Monteil
- Aix-Marseille Université, CEA, CNRS, Institute of Biosciences and Biotechnologies of Aix-Marseille, Saint-Paul-lez-Durance, France
| | - Guy Perrière
- Laboratoire de Biométrie et Biologie Evolutive, Université Claude Bernard-Lyon 1, Villeurbanne, France
| | - Christopher T. Lefèvre
- Aix-Marseille Université, CEA, CNRS, Institute of Biosciences and Biotechnologies of Aix-Marseille, Saint-Paul-lez-Durance, France
| | - Dirk Schüler
- Department of Microbiology, Universitat Bayreuth, Bayreuth, Germany
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2
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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.
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3
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Keren-Khadmy N, Zeytuni N, Kutnowski N, Perriere G, Monteil C, Zarivach R. From conservation to structure, studies of magnetosome associated cation diffusion facilitators (CDF) proteins in Proteobacteria. PLoS One 2020; 15:e0231839. [PMID: 32310978 PMCID: PMC7170241 DOI: 10.1371/journal.pone.0231839] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 04/01/2020] [Indexed: 12/24/2022] Open
Abstract
Magnetotactic bacteria (MTB) are prokaryotes that sense the geomagnetic field lines to geolocate and navigate in aquatic sediments. They are polyphyletically distributed in several bacterial divisions but are mainly represented in the Proteobacteria. In this phylum, magnetotactic Deltaproteobacteria represent the most ancestral class of MTB. Like all MTB, they synthesize membrane-enclosed magnetic nanoparticles, called magnetosomes, for magnetic sensing. Magnetosome biogenesis is a complex process involving a specific set of genes that are conserved across MTB. Two of the most conserved genes are mamB and mamM, that encode for the magnetosome-associated proteins and are homologous to the cation diffusion facilitator (CDF) protein family. In magnetotactic Alphaproteobacteria MTB species, MamB and MamM proteins have been well characterized and play a central role in iron-transport required for biomineralization. However, their structural conservation and their role in more ancestral groups of MTB like the Deltaproteobacteria have not been established. Here we studied magnetite cluster MamB and MamM cytosolic C-terminal domain (CTD) structures from a phylogenetically distant magnetotactic Deltaproteobacteria species represented by BW-1 strain, which has the unique ability to biomineralize magnetite and greigite. We characterized them in solution, analyzed their crystal structures and compared them to those characterized in Alphaproteobacteria MTB species. We showed that despite the high phylogenetic distance, MamBBW-1 and MamMBW-1 CTDs share high structural similarity with known CDF-CTDs and will probably share a common function with the Alphaproteobacteria MamB and MamM.
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Affiliation(s)
- Noa Keren-Khadmy
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Natalie Zeytuni
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Nitzan Kutnowski
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Guy Perriere
- Laboratoire de Biométrie et Biologie Evolutive, UMR CNRS 5558, Université de Lyon, Villeurbanne Cedex, France
| | - Caroline Monteil
- Laboratoire de Biométrie et Biologie Evolutive, UMR CNRS 5558, Université de Lyon, Villeurbanne Cedex, France
- CNRS, CEA, Aix-Marseille Université, UMR7265 Biosciences and Biotechnologies Institute of Aix-Marseille, Saint Paul lez Durance, France
| | - Raz Zarivach
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- * E-mail:
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4
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Choi D, Sonkaria S, Fox SJ, Poudel S, Kim SY, Kang S, Kim S, Verma C, Ahn SH, Lee CS, Khare V. Quantum scale biomimicry of low dimensional growth: An unusual complex amorphous precursor route to TiO 2 band confinement by shape adaptive biopolymer-like flexibility for energy applications. Sci Rep 2019; 9:18721. [PMID: 31822722 PMCID: PMC6904763 DOI: 10.1038/s41598-019-55103-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 11/25/2019] [Indexed: 11/24/2022] Open
Abstract
Crystallization via an amorphous pathway is often preferred by biologically driven processes enabling living species to better regulate activation energies to crystal formation that are intrinsically linked to shape and size of dynamically evolving morphologies. Templated ordering of 3-dimensional space around amorphous embedded non-equilibrium phases at heterogeneous polymer─metal interfaces signify important routes for the genesis of low-dimensional materials under stress-induced polymer confinement. We report the surface induced catalytic loss of P=O ligands to bond activated aromatization of C−C C=C and Ti=N resulting in confinement of porphyrin-TiO2 within polymer nanocages via particle attachment. Restricted growth nucleation of TiO2 to the quantum scale (≤2 nm) is synthetically assisted by nitrogen, phosphine and hydrocarbon polymer chemistry via self-assembly. Here, the amorphous arrest phase of TiO2 is reminiscent of biogenic amorphous crystal growth patterns and polymer coordination has both a chemical and biomimetic significance arising from quantum scale confinement which is atomically challenging. The relative ease in adaptability of non-equilibrium phases renders host structures more shape compliant to congruent guests increasing the possibility of geometrical confinement. Here, we provide evidence for synthetic biomimicry akin to bio-polymerization mechanisms to steer disorder-to-order transitions via solvent plasticization-like behaviour. This challenges the rationale of quantum driven confinement processes by conventional processes. Further, we show the change in optoelectronic properties under quantum confinement is intrinsically related to size that affects their optical absorption band energy range in DSSC.
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Affiliation(s)
- Dahyun Choi
- Department of Materials Engineering, Hanyang University, Ansan, 15588, Republic of Korea
| | - Sanjiv Sonkaria
- Institute of Advanced Machinery and Design, Seoul National University, Daehak-dong, Gwanak-gu, Seoul, 151-742, Republic of Korea
| | - Stephen J Fox
- Bioinformatics Institute (A*STAR), 30 Biopolis Street, #07-01 Matrix, Singapore, 138671, Singapore.,Department of Biological Sciences, National University of Singapore, 16 Science Drive, Singapore, 117558, Singapore.,School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Shivraj Poudel
- Department of Mechanical and Aerospace Engineering, Seoul National University, Daehak-dong, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Sung-Yong Kim
- Department of Mechanical and Aerospace Engineering, Seoul National University, Daehak-dong, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Suhee Kang
- Department of Materials Engineering, Hanyang University, Ansan, 15588, Republic of Korea
| | - Seheon Kim
- Department of Mechanical and Aerospace Engineering, Seoul National University, Daehak-dong, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Chandra Verma
- Bioinformatics Institute (A*STAR), 30 Biopolis Street, #07-01 Matrix, Singapore, 138671, Singapore.,Department of Biological Sciences, National University of Singapore, 16 Science Drive, Singapore, 117558, Singapore.,School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Sung Hoon Ahn
- Institute of Advanced Machinery and Design, Seoul National University, Daehak-dong, Gwanak-gu, Seoul, 151-742, Republic of Korea. .,Department of Mechanical and Aerospace Engineering, Seoul National University, Daehak-dong, Gwanak-gu, Seoul, 08826, Republic of Korea.
| | - Caroline Sunyong Lee
- Department of Materials Engineering, Hanyang University, Ansan, 15588, Republic of Korea.
| | - Varsha Khare
- Department of Materials Engineering, Hanyang University, Ansan, 15588, Republic of Korea.
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Cryo-EM structure of the bacterial actin AlfA reveals unique assembly and ATP-binding interactions and the absence of a conserved subdomain. Proc Natl Acad Sci U S A 2018; 115:3356-3361. [PMID: 29440491 DOI: 10.1073/pnas.1715836115] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacterial actins are an evolutionarily diverse family of ATP-dependent filaments built from protomers with a conserved structural fold. Actin-based segregation systems are encoded on many bacterial plasmids and function to partition plasmids into daughter cells. The bacterial actin AlfA segregates plasmids by a mechanism distinct from other partition systems, dependent on its unique dynamic properties. Here, we report the near-atomic resolution electron cryo-microscopy structure of the AlfA filament, which reveals a strikingly divergent filament architecture resulting from the loss of a subdomain conserved in all other actins and a mode of ATP binding. Its unusual assembly interfaces and nucleotide interactions provide insight into AlfA dynamics, and expand the range of evolutionary variation accessible to actin quaternary structure.
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6
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Tethered Magnets Are the Key to Magnetotaxis: Direct Observations of Magnetospirillum magneticum AMB-1 Show that MamK Distributes Magnetosome Organelles Equally to Daughter Cells. mBio 2017; 8:mBio.00679-17. [PMID: 28790202 PMCID: PMC5550748 DOI: 10.1128/mbio.00679-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Magnetotactic bacteria are a unique group of bacteria that synthesize a magnetic organelle termed the magnetosome, which they use to assist with their magnetic navigation in a specific type of bacterial motility called magneto-aerotaxis. Cytoskeletal filaments consisting of the actin-like protein MamK are associated with the magnetosome chain. Previously, the function of MamK was thought to be in positioning magnetosome organelles; this was proposed based on observations via electron microscopy still images. Here, we conducted live-cell time-lapse fluorescence imaging analyses employing highly inclined and laminated optical sheet microscopy, and these methods enabled us to visualize detailed dynamic movement of magnetosomes in growing cells during the entire cell cycle with high-temporal resolution and a high signal/noise ratio. We found that the MamK cytoskeleton anchors magnetosomes through a mechanism that requires MamK-ATPase activity throughout the cell cycle to prevent simple diffusion of magnetosomes within the cell. We concluded that the static chain-like arrangement of the magnetosomes is required to precisely and consistently segregate the magnetosomes to daughter cells. Thus, the daughter cells inherit a functional magnetic sensor that mediates magneto-reception. Half a century ago, bacterial cells were considered a simple “bag of enzymes”; only recently have they been shown to comprise ordered complexes of macromolecular structures, such as bacterial organelles and cytoskeletons, similar to their eukaryotic counterparts. In eukaryotic cells, the positioning of organelles is regulated by cytoskeletal elements. However, the role of cytoskeletal elements in the positioning of bacterial organelles, such as magnetosomes, remains unclear. Magnetosomes are associated with cytoskeletal filaments that consist of the actin-like protein MamK. In this study, we focused on how the MamK cytoskeleton regulates the dynamic movement of magnetosome organelles in living magnetotactic bacterial cells. Here, we used fluorescence imaging to visualize the dynamics of magnetosomes throughout the cell cycle in living magnetotactic bacterial cells to understand how they use the actin-like cytoskeleton to maintain and to make functional their nano-sized magnetic organelles.
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7
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Sonkaria S, Ahn SH, Lee CS, Khare V. "On the Dot"-The Timing of Self-Assembled Growth to the Quantum Scale. Chemistry 2017; 23:8104-8117. [PMID: 28032925 DOI: 10.1002/chem.201604994] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Indexed: 11/10/2022]
Abstract
Understanding the complex world of material growth and tunability has mystified the minds of material scientists and has been met with increasing efforts to close the gap between controllability and applicability. The reality of this journey is frustratingly tortuous but is being eased through better conceptual appreciation of metal crystalline frameworks that originate from shape and size dependent solvent responsive growth patterns. The quantum confinement of TiO2 in the range of 0.8-2 nm has been synthetically challenging to achieve but lessons from biomineralization processes have enabled alternative routes to be explored via self-induced pre-nucleation events. In driving this concept, we have incorporated many of these key features integrating aspects of low temperature annealing at the interface of complex heterogeneous nucleation between hard and soft materials to arrest the biomimetic amorphous phase of TiO2 to a tunable crystalline quantumized state. The stabilization of metastable states of quantum sized TiO2 driven by kinetic and thermodynamic processes show hallmarks of biomineralized controlled events that suggest the inter-play between new pathways and interfacial energies that preferentially favor low dimensionality at the quantum scale. This provides the potential to re-direct synthetic assemblies under tightly controlled parameters to generate a host of new materials with size, shape and anisotropic properties as smart stimuli responsive materials. These new stabilities leading to the growth arrest of TiO2 are discussed in terms of molecular interactions and structural frameworks that were previously inaccessible via conventional routes. There exists an undiscovered parallel between synthetic and biomineralized routes enabling unprecedented access to the availability and tunability of novel quantum confined materials. The parametrics of complex material design at the crossroads of synthetically and biologically driven processes is only now surfacing.
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Affiliation(s)
- Sanjiv Sonkaria
- Institute of Advanced Machinery and Design, Seoul National University, Gwanak Ro1, Seoul, Republic of Korea
| | - Sung-Hoon Ahn
- Institute of Advanced Machinery and Design, Seoul National University, Gwanak Ro1, Seoul, Republic of Korea.,Department of Mechanical and Aerospace Engineering, Seoul National University, Gwanak Ro1, Seoul, Republic of Korea
| | - Caroline S Lee
- Department of Materials Engineering, Hanyang University, Gyeongi, Ansan, 426-791, Republic of Korea
| | - Varsha Khare
- Institute of Advanced Machinery and Design, Seoul National University, Gwanak Ro1, Seoul, Republic of Korea
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8
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Abstract
Magnetotactic bacteria derive their magnetic orientation from magnetosomes, which are unique organelles that contain nanometre-sized crystals of magnetic iron minerals. Although these organelles have evident potential for exciting biotechnological applications, a lack of genetically tractable magnetotactic bacteria had hampered the development of such tools; however, in the past decade, genetic studies using two model Magnetospirillum species have revealed much about the mechanisms of magnetosome biogenesis. In this Review, we highlight these new insights and place the molecular mechanisms of magnetosome biogenesis in the context of the complex cell biology of Magnetospirillum spp. Furthermore, we discuss the diverse properties of magnetosome biogenesis in other species of magnetotactic bacteria and consider the value of genetically 'magnetizing' non-magnetotactic bacteria. Finally, we discuss future prospects for this highly interdisciplinary and rapidly advancing field.
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9
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Barber-Zucker S, Zarivach R. A Look into the Biochemistry of Magnetosome Biosynthesis in Magnetotactic Bacteria. ACS Chem Biol 2017; 12:13-22. [PMID: 27930882 DOI: 10.1021/acschembio.6b01000] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Magnetosomes are protein-rich membrane organelles that encapsulate magnetite or greigite and whose chain alignment enables magnetotactic bacteria (MTB) to sense the geomagnetic field. As these bacteria synthesize uniform magnetic particles, their biomineralization mechanism is of great interest among researchers from different fields, from material engineering to medicine. Both magnetosome formation and magnetic particle synthesis are highly controlled processes that can be divided into several crucial steps: membrane invagination from the inner-cell membrane, protein sorting, the magnetosomes' arrangement into chains, iron transport, chemical environment regulation of the magnetosome lumen, magnetic particle nucleation, and finally crystal growth, size, and morphology control. This complex system involves an ensemble of unique proteins that participate in different stages during magnetosome formation, some of which were extensively studied in recent years. Here, we present the current knowledge on magnetosome biosynthesis with a focus on the different proteins and the main biochemical pathways along this process.
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Affiliation(s)
- Shiran Barber-Zucker
- Department of Life
Sciences,
the National Institute for Biotechnology in the Negev and Ilse Katz
Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, 8410501, Israel
| | - Raz Zarivach
- Department of Life
Sciences,
the National Institute for Biotechnology in the Negev and Ilse Katz
Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, 8410501, Israel
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10
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Abstract
A diverse set of protein polymers, structurally related to actin filaments contributes to the organization of bacterial cells as cytomotive or cytoskeletal filaments. This chapter describes actin homologs encoded by bacterial chromosomes. MamK filaments, unique to magnetotactic bacteria, help establishing magnetic biological compasses by interacting with magnetosomes. Magnetosomes are intracellular membrane invaginations containing biomineralized crystals of iron oxide that are positioned by MamK along the long-axis of the cell. FtsA is widespread across bacteria and it is one of the earliest components of the divisome to arrive at midcell, where it anchors the cell division machinery to the membrane. FtsA binds directly to FtsZ filaments and to the membrane through its C-terminus. FtsA shows altered domain architecture when compared to the canonical actin fold. FtsA's subdomain 1C replaces subdomain 1B of other members of the actin family and is located on the opposite side of the molecule. Nevertheless, when FtsA assembles into protofilaments, the protofilament structure is preserved, as subdomain 1C replaces subdomain IB of the following subunit in a canonical actin filament. MreB has an essential role in shape-maintenance of most rod-shaped bacteria. Unusually, MreB filaments assemble from two protofilaments in a flat and antiparallel arrangement. This non-polar architecture implies that both MreB filament ends are structurally identical. MreB filaments bind directly to membranes where they interact with both cytosolic and membrane proteins, thereby forming a key component of the elongasome. MreB filaments in cells are short and dynamic, moving around the long axis of rod-shaped cells, sensing curvature of the membrane and being implicated in peptidoglycan synthesis.
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Affiliation(s)
- Thierry Izoré
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Fusinita van den Ent
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
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11
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Bergeron JRC, Hutto R, Ozyamak E, Hom N, Hansen J, Draper O, Byrne ME, Keyhani S, Komeili A, Kollman JM. Structure of the magnetosome-associated actin-like MamK filament at subnanometer resolution. Protein Sci 2016; 26:93-102. [PMID: 27391173 DOI: 10.1002/pro.2979] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 06/16/2016] [Accepted: 06/22/2016] [Indexed: 11/11/2022]
Abstract
Magnetotactic bacteria possess cellular compartments called magnetosomes that sense magnetic fields. Alignment of magnetosomes in the bacterial cell is necessary for their function, and this is achieved through anchoring of magnetosomes to filaments composed of the protein MamK. MamK is an actin homolog that polymerizes upon ATP binding. Here, we report the structure of the MamK filament at ∼6.5 Å, obtained by cryo-Electron Microscopy. This structure confirms our previously reported double-stranded, nonstaggered architecture, and reveals the molecular basis for filament formation. While MamK is closest in sequence to the bacterial actin MreB, the longitudinal contacts along each MamK strand most closely resemble those of eukaryotic actin. In contrast, the cross-strand interface, with a surprisingly limited set of contacts, is novel among actin homologs and gives rise to the nonstaggered architecture.
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Affiliation(s)
| | - Rachel Hutto
- Department of Biochemistry, University of Washington, Seattle, Washington
| | - Ertan Ozyamak
- Department of Plant and Microbial Biology, University of California, Berkeley, California
| | - Nancy Hom
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington
| | - Jesse Hansen
- Department of Biochemistry, University of British Columbia, Vancouver, British Columbia
| | - Olga Draper
- Department of Plant and Microbial Biology, University of California, Berkeley, California
| | - Meghan E Byrne
- Department of Plant and Microbial Biology, University of California, Berkeley, California
| | - Sepehr Keyhani
- Department of Plant and Microbial Biology, University of California, Berkeley, California
| | - Arash Komeili
- Department of Plant and Microbial Biology, University of California, Berkeley, California
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, Washington
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12
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Deng A, Lin W, Shi N, Wu J, Sun Z, Sun Q, Bai H, Pan Y, Wen T. In vitro assembly of the bacterial actin protein MamK from ' Candidatus Magnetobacterium casensis' in the phylum Nitrospirae. Protein Cell 2016; 7:267-280. [PMID: 26960409 PMCID: PMC4818849 DOI: 10.1007/s13238-016-0253-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 02/07/2016] [Indexed: 10/29/2022] Open
Abstract
Magnetotactic bacteria (MTB), a group of phylogenetically diverse organisms that use their unique intracellular magnetosome organelles to swim along the Earth's magnetic field, play important roles in the biogeochemical cycles of iron and sulfur. Previous studies have revealed that the bacterial actin protein MamK plays essential roles in the linear arrangement of magnetosomes in MTB cells belonging to the Proteobacteria phylum. However, the molecular mechanisms of multiple-magnetosome-chain arrangements in MTB remain largely unknown. Here, we report that the MamK filaments from the uncultivated 'Candidatus Magnetobacterium casensis' (Mcas) within the phylum Nitrospirae polymerized in the presence of ATP alone and were stable without obvious ATP hydrolysis-mediated disassembly. MamK in Mcas can convert NTP to NDP and NDP to NMP, showing the highest preference to ATP. Unlike its Magnetospirillum counterparts, which form a single magnetosome chain, or other bacterial actins such as MreB and ParM, the polymerized MamK from Mcas is independent of metal ions and nucleotides except for ATP, and is assembled into well-ordered filamentous bundles consisted of multiple filaments. Our results suggest a dynamically stable assembly of MamK from the uncultivated Nitrospirae MTB that synthesizes multiple magnetosome chains per cell. These findings further improve the current knowledge of biomineralization and organelle biogenesis in prokaryotic systems.
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Affiliation(s)
- Aihua Deng
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wei Lin
- Biogeomagnetism Group, Paleomagnetism and Geochronology Laboratory, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
| | - Nana Shi
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jie Wu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhaopeng Sun
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qinyun Sun
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hua Bai
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yongxin Pan
- Biogeomagnetism Group, Paleomagnetism and Geochronology Laboratory, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
| | - Tingyi Wen
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
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13
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Faivre D, Godec TU. From bacteria to mollusks: the principles underlying the biomineralization of iron oxide materials. Angew Chem Int Ed Engl 2016; 54:4728-47. [PMID: 25851816 DOI: 10.1002/anie.201408900] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Indexed: 01/28/2023]
Abstract
Various organisms possess a genetic program that enables the controlled formation of a mineral, a process termed biomineralization. The variety of biological material architectures is mind-boggling and arises from the ability of organisms to exert control over crystal nucleation and growth. The structure and composition of biominerals equip biomineralizing organisms with properties and functionalities that abiotically formed materials, made of the same mineral, usually lack. Therefore, elucidating the mechanisms underlying biomineralization and morphogenesis is of interdisciplinary interest to extract design principles that will enable the biomimetic formation of functional materials with similar capabilities. Herein, we summarize what is known about iron oxides formed by bacteria and mollusks for their magnetic and mechanical properties. We describe the chemical and biological machineries that are involved in controlling mineral precipitation and organization and show how these organisms are able to form highly complex structures under physiological conditions.
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Affiliation(s)
- Damien Faivre
- Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Wissenschaftspark Golm, 14424 Potsdam (Germany) http://www.mpikg.mpg.de/135282/MBMB.
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14
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Barber-Zucker S, Keren-Khadmy N, Zarivach R. From invagination to navigation: The story of magnetosome-associated proteins in magnetotactic bacteria. Protein Sci 2015; 25:338-51. [PMID: 26457474 DOI: 10.1002/pro.2827] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 10/07/2015] [Indexed: 11/11/2022]
Abstract
Magnetotactic bacteria (MTB) are a group of Gram-negative microorganisms that are able to sense and change their orientation in accordance with the geomagnetic field. This unique capability is due to the presence of a special suborganelle called the magnetosome, composed of either a magnetite or gregite crystal surrounded by a lipid membrane. MTB were first detected in 1975 and since then numerous efforts have been made to clarify the special mechanism of magnetosome formation at the molecular level. Magnetosome formation can be divided into several steps, beginning with vesicle invagination from the cell membrane, through protein sorting, followed by the combined steps of iron transportation, biomineralization, and the alignment of magnetosomes into a chain. The magnetosome-chain enables the sensing of the magnetic field, and thus, allows the MTB to navigate. It is known that magnetosome formation is tightly controlled by a distinctive set of magnetosome-associated proteins that are encoded mainly in a genomically conserved region within MTB called the magnetosome island (MAI). Most of these proteins were shown to have an impact on the magnetism of MTB. Here, we describe the process in which the magnetosome is formed with an emphasis on the different proteins that participate in each stage of the magnetosome formation scheme.
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Affiliation(s)
- Shiran Barber-Zucker
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, 8410501, Israel
| | - Noa Keren-Khadmy
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, 8410501, Israel
| | - Raz Zarivach
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, 8410501, Israel
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15
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Faivre D, Godec TU. Bakterien und Weichtiere: Prinzipien der Biomineralisation von Eisenoxid-Materialien. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201408900] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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16
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Bennet M, Bertinetti L, Neely RK, Schertel A, Körnig A, Flors C, Müller FD, Schüler D, Klumpp S, Faivre D. Biologically controlled synthesis and assembly of magnetite nanoparticles. Faraday Discuss 2015; 181:71-83. [PMID: 25932467 PMCID: PMC4672721 DOI: 10.1039/c4fd00240g] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 12/23/2014] [Indexed: 11/21/2022]
Abstract
Magnetite nanoparticles have size- and shape-dependent magnetic properties. In addition, assemblies of magnetite nanoparticles forming one-dimensional nanostructures have magnetic properties distinct from zero-dimensional or non-organized materials due to strong uniaxial shape anisotropy. However, assemblies of free-standing magnetic nanoparticles tend to collapse and form closed-ring structures rather than chains in order to minimize their energy. Magnetotactic bacteria, ubiquitous microorganisms, have the capability to mineralize magnetite nanoparticles, the so-called magnetosomes, and to direct their assembly in stable chains via biological macromolecules. In this contribution, the synthesis and assembly of biological magnetite to obtain functional magnetic dipoles in magnetotactic bacteria are presented, with a focus on the assembly. We present tomographic reconstructions based on cryo-FIB sectioning and SEM imaging of a magnetotactic bacterium to exemplify that the magnetosome chain is indeed a paradigm of a 1D magnetic nanostructure, based on the assembly of several individual particles. We show that the biological forces are a major player in the formation of the magnetosome chain. Finally, we demonstrate by super resolution fluorescence microscopy that MamK, a protein of the actin family necessary to form the chain backbone in the bacteria, forms a bundle of filaments that are not only found in the vicinity of the magnetosome chain but are widespread within the cytoplasm, illustrating the dynamic localization of the protein within the cells. These very simple microorganisms have thus much to teach us with regards to controlling the design of functional 1D magnetic nanoassembly.
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Affiliation(s)
- Mathieu Bennet
- Department of Biomaterials , Max Planck Institute of Colloids and Interfaces , Science Park Golm , 14424 Potsdam , Germany .
| | - Luca Bertinetti
- Department of Biomaterials , Max Planck Institute of Colloids and Interfaces , Science Park Golm , 14424 Potsdam , Germany .
| | - Robert K. Neely
- The University of Birmingham , School of Chemistry , Edgbaston , Birmingham , B15 2TT , UK
| | - Andreas Schertel
- Carl Zeiss Microscopy GmbH , Training , Application and Support Center , Carl-Zeiss-Str. 22 , 73447 Oberkochen , Germany
| | - André Körnig
- Department of Biomaterials , Max Planck Institute of Colloids and Interfaces , Science Park Golm , 14424 Potsdam , Germany .
| | - Cristina Flors
- Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanociencia) , C/Faraday 9 , Madrid 28049 , Spain
| | - Frank D. Müller
- Universität Bayreuth , Lehrstuhl für Mikrobiologie , Universitätssstraße 30 , 95447 Bayreuth , Germany
| | - Dirk Schüler
- Universität Bayreuth , Lehrstuhl für Mikrobiologie , Universitätssstraße 30 , 95447 Bayreuth , Germany
| | - Stefan Klumpp
- Department of Theory and Biosystems , Max Planck Institute of Colloids and Interfaces , Science Park Golm , 14424 Potsdam , Germany
| | - Damien Faivre
- Department of Biomaterials , Max Planck Institute of Colloids and Interfaces , Science Park Golm , 14424 Potsdam , Germany .
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Körnig A, Dong J, Bennet M, Widdrat M, Andert J, Müller F, Schüler D, Klumpp S, Faivre D. Probing the mechanical properties of magnetosome chains in living magnetotactic bacteria. NANO LETTERS 2014; 14:4653-9. [PMID: 25003507 PMCID: PMC4133184 DOI: 10.1021/nl5017267] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The mechanical properties of cytoskeletal networks are intimately involved in determining how forces and cellular processes are generated, directed, and transmitted in living cells. However, determining the mechanical properties of subcellular molecular complexes in vivo has proven to be difficult. Here, we combine in vivo measurements by optical microscopy, X-ray diffraction, and transmission electron microscopy with theoretical modeling to decipher the mechanical properties of the magnetosome chain system encountered in magnetotactic bacteria. We exploit the magnetic properties of the endogenous intracellular nanoparticles to apply a force on the filament-connector pair involved in the backbone formation and stabilization. We show that the magnetosome chain can be broken by the application of external field strength higher than 30 mT and suggest that this originates from the rupture of the magnetosome connector MamJ. In addition, we calculate that the biological determinants can withstand in vivo a force of 25 pN. This quantitative understanding provides insights for the design of functional materials such as actuators and sensors using cellular components.
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Affiliation(s)
- André Körnig
- Department of Biomaterials and Department of
Theory and Bio-Systems, Max Planck Institute
of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
| | - Jiajia Dong
- Department of Biomaterials and Department of
Theory and Bio-Systems, Max Planck Institute
of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
- Department
of Physics and Astronomy, Bucknell University, Lewisburg, Pennsylvania 17837, United States
| | - Mathieu Bennet
- Department of Biomaterials and Department of
Theory and Bio-Systems, Max Planck Institute
of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
| | - Marc Widdrat
- Department of Biomaterials and Department of
Theory and Bio-Systems, Max Planck Institute
of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
| | - Janet Andert
- Department of Biomaterials and Department of
Theory and Bio-Systems, Max Planck Institute
of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
| | - Frank
D. Müller
- Department
1, Microbiology, Ludwig-Maximilians-Universität
München, Großhaderner
Strasse 2-4, 82152 Planegg-Martinsried, Germany
| | - Dirk Schüler
- Department
1, Microbiology, Ludwig-Maximilians-Universität
München, Großhaderner
Strasse 2-4, 82152 Planegg-Martinsried, Germany
| | - Stefan Klumpp
- Department of Biomaterials and Department of
Theory and Bio-Systems, Max Planck Institute
of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
| | - Damien Faivre
- Department of Biomaterials and Department of
Theory and Bio-Systems, Max Planck Institute
of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
- (D.F.)
E-mail:
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Arnoux P, Siponen MI, Lefèvre CT, Ginet N, Pignol D. Structure and evolution of the magnetochrome domains: no longer alone. Front Microbiol 2014; 5:117. [PMID: 24723915 PMCID: PMC3971196 DOI: 10.3389/fmicb.2014.00117] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 03/08/2014] [Indexed: 11/13/2022] Open
Abstract
Magnetotactic bacteria (MTB) can swim along Earth's magnetic field lines, thanks to the alignment of dedicated cytoplasmic organelles. These organelles, termed magnetosomes, are proteolipidic vesicles filled by a 35–120 nm crystal of either magnetite or greigite. The formation and alignment of magnetosomes are mediated by a group of specific genes, the mam genes, encoding the magnetosome-associated proteins. The whole process of magnetosome biogenesis can be divided into four sequential steps; (i) cytoplasmic membrane invagination, (ii) magnetosomes alignment, (iii) iron crystal nucleation and (iv) species-dependent mineral size and shape control. Since both magnetite and greigite are a mix of iron (III) and iron (II), iron redox state management within the magnetosome vesicle is a key issue. Recently, studies have started pointing out the importance of a MTB-specific c-type cytochrome domain found in several magnetosome-associated proteins (MamE, P, T, and X). This magnetochrome (MCR) domain is almost always found in tandem, and this tandem is either found alone (MamT), in combination with a PDZ domain (MamP), a domain of unknown function (MamX) or with a trypsin combined to one or two PDZ domains (MamE). By taking advantage of new genomic data available on MTB and a recent structural study of MamP, which helped define the MCR domain boundaries, we attempt to retrace the evolutionary history within and between the different MCR-containing proteins. We propose that the observed tandem repeat of MCR is the result of a convergent evolution and attempt to explain why this domain is rarely found alone.
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Affiliation(s)
- Pascal Arnoux
- Commissariat à l'énergie Atomique, DSV, IBEB, Lab Bioenerget Cellulaire Saint-Paul-lez-Durance, France ; Centre National de la Recherche Scientifique, UMR Biol Veget and Microbiol Environ Saint-Paul-lez-Durance, France ; Aix-Marseille Université Saint-Paul-lez-Durance, France
| | - Marina I Siponen
- Commissariat à l'énergie Atomique, DSV, IBEB, Lab Bioenerget Cellulaire Saint-Paul-lez-Durance, France ; Centre National de la Recherche Scientifique, UMR Biol Veget and Microbiol Environ Saint-Paul-lez-Durance, France ; Aix-Marseille Université Saint-Paul-lez-Durance, France
| | - Christopher T Lefèvre
- Commissariat à l'énergie Atomique, DSV, IBEB, Lab Bioenerget Cellulaire Saint-Paul-lez-Durance, France ; Centre National de la Recherche Scientifique, UMR Biol Veget and Microbiol Environ Saint-Paul-lez-Durance, France ; Aix-Marseille Université Saint-Paul-lez-Durance, France
| | - Nicolas Ginet
- Commissariat à l'énergie Atomique, DSV, IBEB, Lab Bioenerget Cellulaire Saint-Paul-lez-Durance, France ; Centre National de la Recherche Scientifique, UMR Biol Veget and Microbiol Environ Saint-Paul-lez-Durance, France ; Aix-Marseille Université Saint-Paul-lez-Durance, France
| | - David Pignol
- Commissariat à l'énergie Atomique, DSV, IBEB, Lab Bioenerget Cellulaire Saint-Paul-lez-Durance, France ; Centre National de la Recherche Scientifique, UMR Biol Veget and Microbiol Environ Saint-Paul-lez-Durance, France ; Aix-Marseille Université Saint-Paul-lez-Durance, France
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Nudelman H, Zarivach R. Structure prediction of magnetosome-associated proteins. Front Microbiol 2014; 5:9. [PMID: 24523717 PMCID: PMC3905215 DOI: 10.3389/fmicb.2014.00009] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 01/08/2014] [Indexed: 01/23/2023] Open
Abstract
Magnetotactic bacteria (MTB) are Gram-negative bacteria that can navigate along geomagnetic fields. This ability is a result of a unique intracellular organelle, the magnetosome. These organelles are composed of membrane-enclosed magnetite (Fe3O4) or greigite (Fe3S4) crystals ordered into chains along the cell. Magnetosome formation, assembly, and magnetic nano-crystal biomineralization are controlled by magnetosome-associated proteins (MAPs). Most MAP-encoding genes are located in a conserved genomic region – the magnetosome island (MAI). The MAI appears to be conserved in all MTB that were analyzed so far, although the MAI size and organization differs between species. It was shown that MAI deletion leads to a non-magnetic phenotype, further highlighting its important role in magnetosome formation. Today, about 28 proteins are known to be involved in magnetosome formation, but the structures and functions of most MAPs are unknown. To reveal the structure–function relationship of MAPs we used bioinformatics tools in order to build homology models as a way to understand their possible role in magnetosome formation. Here we present a predicted 3D structural models’ overview for all known Magnetospirillum gryphiswaldense strain MSR-1 MAPs.
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Affiliation(s)
- Hila Nudelman
- Department of Life Sciences, Ben-Gurion University of the Negev Beer Sheva, Israel ; National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev Beer Sheva, Israel
| | - Raz Zarivach
- Department of Life Sciences, Ben-Gurion University of the Negev Beer Sheva, Israel ; National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev Beer Sheva, Israel
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20
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Cornejo E, Abreu N, Komeili A. Compartmentalization and organelle formation in bacteria. Curr Opin Cell Biol 2014; 26:132-8. [PMID: 24440431 DOI: 10.1016/j.ceb.2013.12.007] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 12/17/2013] [Accepted: 12/17/2013] [Indexed: 12/19/2022]
Abstract
A number of bacterial species rely on compartmentalization to gain specific functionalities that will provide them with a selective advantage. Here, we will highlight several of these modes of bacterial compartmentalization with an eye toward describing the mechanisms of their formation and their evolutionary origins. Spore formation in Bacillus subtilis, outer membrane biogenesis in Gram-negative bacteria and protein diffusion barriers of Caulobacter crescentus will be used to demonstrate the physical, chemical, and compositional remodeling events that lead to compartmentalization. In addition, magnetosomes and carboxysomes will serve as models to examine the interplay between cytoskeletal systems and the subcellular positioning of organelles.
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Affiliation(s)
- Elias Cornejo
- Department of Plant and Microbial Biology, University of California, Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102, United States
| | - Nicole Abreu
- Department of Plant and Microbial Biology, University of California, Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102, United States
| | - Arash Komeili
- Department of Plant and Microbial Biology, University of California, Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102, United States.
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21
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Abstract
For many years, bacteria were considered rather simple organisms, but the dogmatic notion that subcellular organization is a eukaryotic trait has been overthrown for more than a decade. The discovery of homologues of the eukaryotic cytoskeletal proteins actin, tubulin, and intermediate filaments in bacteria has been instrumental in changing this view. Over the past few years, we have gained an incredible level of insight into the diverse family of bacterial actins and their molecular workings. Here we review the functional, biochemical, and structural features of the most well-studied bacterial actins.
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Affiliation(s)
- Ertan Ozyamak
- Department of Plant and Microbial Biology, University of California , Berkeley, California 94720, United States
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22
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MamX encoded by the mamXY operon is involved in control of magnetosome maturation in Magnetospirillum gryphiswaldense MSR-1. BMC Microbiol 2013; 13:203. [PMID: 24020498 PMCID: PMC3847676 DOI: 10.1186/1471-2180-13-203] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 09/03/2013] [Indexed: 12/15/2022] Open
Abstract
Background Magnetotactic bacteria produce membrane-enveloped magnetite crystals (magnetosomes) whose formation is controlled primarily by a gene island termed the magnetosome island (MAI). Characterization of single gene and operon function in MAI has elucidated in part the genetic basis of magnetosome formation. The mamX gene, located in the mamXY operon, is highly conserved in the MAI of all Magnetospirillum strains studied to date. Little is known regarding the function of mamX in the process of biomineralization. Results A mamX deletion mutant (∆mamX) and its complemented strain (CmamX) by conjugation in M. gryphiswaldense strain MSR-1 were constructed. There were no striking differences in cell growth among ∆mamX, CmamX, and wild-type strain (WT). ∆mamX displayed a much weaker magnetic response than WT. Transmission electron microscopy revealed the presence of irregular, superparamagnetic magnetite particles in ∆mamX, in contrast to regular, single-domain particles in WT and CmamX. The phenotype of ∆mamX was similar to that of an ftsZ-like deleted mutant and mamXY operon deleted mutant reported previously. Quantitative real-time RT-PCR (qPCR) results indicated that the deletion of mamX had differential effects on the transcription levels of the other three genes in the operon. Conclusions The MamX protein plays an important role in controlling magnetosome size, maturation, and crystal form. The four MamXY proteins appear to have redundant functions involved in magnetosome formation. Our findings provide new insights into the coordinated function of MAI genes and operons in magnetosome formation.
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Yang J, Li S, Huang X, Tang T, Jiang W, Zhang T, Li Y. A key time point for cell growth and magnetosome synthesis of Magnetospirillum gryphiswaldense based on real-time analysis of physiological factors. Front Microbiol 2013; 4:210. [PMID: 23898327 PMCID: PMC3721002 DOI: 10.3389/fmicb.2013.00210] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Accepted: 07/07/2013] [Indexed: 12/24/2022] Open
Abstract
Pure culture of magnetotactic bacteria with high magnetosome yield has been achieved for only a few strains. The major obstacles involve the nutritional requirements and culture conditions of the cells. To increase cell density and magnetosome production, it is necessary to elucidate the physiological characteristics of a particular strain during cell growth and develop an appropriate artificial control strategy. Large-scale culture of Magnetospirillum gryphiswaldense strain MSR-1 was successfully performed for 48 h in a 42-L autofermentor, and several key physiological parameters were measured in real time. Maximal values of cell density (OD565) (19.4) and cell yield (dry weight) (4.76 g/L) were attained at 40 h. The key time point for cell growth and magnetosome formation was found to be 18–20 h. At this point, cells entered the log phase of growth, the maximal values of Cmag (1.78), iron content (0.47%), and magnetosome number (26 ± 3 per cell) were observed, superoxide dismutase (SOD) activity began to decrease more rapidly, ATP content dropped to an extremely low level (0.17 fmol), and reducing power (NADH/NAD+ ratio) began to increase very rapidly. Excessive levels of dissolved oxygen (≥20 ppb) and lactic acid in the medium caused notable cytotoxic effects after 20 h. Artificial control measures for fermentation must be based on realistic cell physiological conditions. At the key time point (18–20 h), cell density is high and magnetosomes have matured. The process of magnetosome synthesis involves a high consumption of ATP and reducing power, and the cells require replenishment of nutrients prior to the 18–20 h time point. Culture conditions that effectively minimize dissolved oxygen accumulation, lactic acid content, and reducing power at this point will enhance magnetosome yield without obvious inhibition of cell growth.
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Affiliation(s)
- Jing Yang
- Key Laboratory of Agro-biotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University Beijing, China ; France-China Biomineralization and Nano-structure Laboratory Beijing, China
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Kalirai SS, Bazylinski DA, Hitchcock AP. Anomalous magnetic orientations of magnetosome chains in a magnetotactic bacterium: Magnetovibrio blakemorei strain MV-1. PLoS One 2013; 8:e53368. [PMID: 23308202 PMCID: PMC3540082 DOI: 10.1371/journal.pone.0053368] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Accepted: 11/30/2012] [Indexed: 11/19/2022] Open
Abstract
There is a good deal of published evidence that indicates that all magnetosomes within a single cell of a magnetotactic bacterium are magnetically oriented in the same direction so that they form a single magnetic dipole believed to assist navigation of the cell to optimal environments for their growth and survival. Some cells of the cultured magnetotactic bacterium Magnetovibrio blakemorei strain MV-1 are known to have relatively wide gaps between groups of magnetosomes that do not seem to interfere with the larger, overall linear arrangement of the magnetosomes along the long axis of the cell. We determined the magnetic orientation of the magnetosomes in individual cells of this bacterium using Fe 2p X-ray magnetic circular dichroism (XMCD) spectra measured with scanning transmission X-ray microscopy (STXM). We observed a significant number of cases in which there are sub-chains in a single cell, with spatial gaps between them, in which one or more sub-chains are magnetically polarized opposite to other sub-chains in the same cell. These occur with an estimated frequency of 4.0±0.2%, based on a sample size of 150 cells. We propose possible explanations for these anomalous cases which shed insight into the mechanisms of chain formation and magnetic alignment.
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Affiliation(s)
- Samanbir S. Kalirai
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
| | - Dennis A. Bazylinski
- School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, Nevada, United States of America
| | - Adam P. Hitchcock
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
- * E-mail:
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Ozyamak E, Kollman J, Agard DA, Komeili A. The bacterial actin MamK: in vitro assembly behavior and filament architecture. J Biol Chem 2012. [PMID: 23204522 DOI: 10.1074/jbc.m112.417030] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
It is now recognized that actin-like proteins are widespread in bacteria and, in contrast to eukaryotic actins, are highly diverse in sequence and function. The bacterial actin, MamK, represents a clade, primarily found in magnetotactic bacteria, that is involved in the proper organization of subcellular organelles, termed magnetosomes. We have previously shown that MamK from Magnetospirillum magneticum AMB-1 (AMB-1) forms dynamic filaments in vivo. To gain further insights into the molecular mechanisms that underlie MamK dynamics and function, we have now studied the in vitro properties of MamK. We demonstrate that MamK is an ATPase that, in the presence of ATP, assembles rapidly into filaments that disassemble once ATP is depleted. The mutation of a conserved active site residue (E143A) abolishes ATPase activity of MamK but not its ability to form filaments. Filament disassembly depends on both ATPase activity and potassium levels, the latter of which results in the organization of MamK filaments into bundles. These data are consistent with observations indicating that accessory factors are required to promote filament disassembly and for spatial organization of filaments in vivo. We also used cryo-electron microscopy to obtain a high resolution structure of MamK filaments. MamK adopts a two-stranded helical filament architecture, but unlike eukaryotic actin and other actin-like filaments, subunits in MamK strands are unstaggered giving rise to a unique filament architecture. Beyond extending our knowledge of the properties and function of MamK in magnetotactic bacteria, this study emphasizes the functional and structural diversity of bacterial actins in general.
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Affiliation(s)
- Ertan Ozyamak
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA
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Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness. Proc Natl Acad Sci U S A 2012; 109:16923-7. [PMID: 23027950 DOI: 10.1073/pnas.1211078109] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as "polymerization" and "stiffness" sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments.
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