The Experts below are selected from a list of 6369 Experts worldwide ranked by ideXlab platform

Sonja-verena Albers - One of the best experts on this subject based on the ideXlab platform.

  • Archaeal sepf is essential for Cell division in haloferax volcanii
    bioRxiv, 2020
    Co-Authors: Phillip Nussbaum, M K Gerstner, M Dingethal, C Erb, Sonja-verena Albers
    Abstract:

    Bacterial Cell division has been studied for decades but reports on the different Archaeal Cell division systems are rare. In many archaea, Cell division depends on the tubulin homolog FtsZ, but further components of the divisome in these archaea are unknown. The halophilic archaeon Haloferax volcanii encodes two FtsZ homologs with different functions in Cell division and a putative SepF homolog. In bacteria, SepF is part of the divisome and is recruited early to the FtsZ ring, where it most likely stimulates FtsZ ring formation. H. volcanii SepF co-localized with FtsZ1 and FtsZ2 at midCell. Overexpression of SepF had no effect on Cell morphology, but no sepF deletion mutants could be generated. SepF depletion led to a severe Cell division defect, resulting in Cells with a strongly increased size. Overexpression of FtsZ1- and FtsZ2-GFP in SepF-depleted Cells resulted in filamentous Cells with an increasing number of FtsZ1 rings depending on the Cell length, whereas FtsZ2 rings were not increased. Pull-down assays with HA-tagged SepF identified an interaction with FtsZ2 but not with FtsZ1. Archaeal SepF homologs lack the conserved glycine residue important for polymerization in bacteria and the H. volcanii SepF was purified as a dimer, suggesting that in contrast to the bacterial SepF homologs, polymerization does not seem to be important for its function. A model is proposed where first the FtsZ1 ring is formed and where SepF recruits FtsZ2 to the FtsZ1 ring, resulting in the formation of the FtsZ2 ring. This study provides important novel insights into Cell division in archaea and shows that SepF is an important part of the divisome in FtsZ containing archaea.

  • architecture and modular assembly of sulfolobus s layers revealed by electron cryotomography
    Proceedings of the National Academy of Sciences of the United States of America, 2019
    Co-Authors: Lavinia Gambelli, Sonja-verena Albers, Tessa E F Quax, Benjamin Meyer, Mathew Mclaren, Kelly Sanders, Vicki A M Gold, Bertram Daum
    Abstract:

    Surface protein layers (S-layers) often form the only structural component of the Archaeal Cell wall and are therefore important for Cell survival. S-layers have a plethora of Cellular functions including maintenance of Cell shape, osmotic, and mechanical stability, the formation of a semipermeable protective barrier around the Cell, and Cell–Cell interaction, as well as surface adhesion. Despite the central importance of S-layers for Archaeal life, their 3-dimensional (3D) architecture is still poorly understood. Here we present detailed 3D electron cryomicroscopy maps of Archaeal S-layers from 3 different Sulfolobus strains. We were able to pinpoint the positions and determine the structure of the 2 subunits SlaA and SlaB. We also present a model describing the assembly of the mature S-layer.

  • editorial Archaeal Cell envelope and surface structures
    Frontiers in Microbiology, 2016
    Co-Authors: Mechthild Pohlschroder, Sonja-verena Albers
    Abstract:

    Archaea and Bacteria have complex Cell envelopes that play important roles in several vital Cellular processes, including serving as a barrier that protects the cytoplasm from the environment. Along with associated proteinaceous structures, Cell envelopes also ensure Cell stability, promote motility, mediate adherence to biotic and abiotic surfaces, and facilitate communication with the extraCellular environment. While some aspects of the biosynthesis and structure of the Cell envelope are similar across the three domains of life, Archaeal Cell envelopes exhibit several unique characteristics. Moreover, recent analyses have revealed that many features of Cell envelopes can vary greatly between distantly related archaea. The collection of reviews and original research papers in this focused issue describes research that has significantly expanded our understanding of the mechanisms underlying the biogenesis and functions of Archaeal Cell envelopes and their constituent surface structures.

  • Archaeal Cell walls
    eLS, 2014
    Co-Authors: Benjamin H. Meyer, Sonja-verena Albers
    Abstract:

    Next to the bacterial and eukaryal domains, Archaea form the third domain of life. One major difference to bacteria is the composition of the Cell wall. The Cell wall of most Archaea is formed by a proteinaceous surface (S-) layer. S-layer proteins have the intrinsic ability to form two-dimensional crystals, which can have an oblique (p2), square (p4) or hexagonal (p3 or p6) symmetry. All currently studied Archaeal S-layer proteins were found to be modified by the attachment of N-linked and, in some cases, additionally by O-linked glycans. Next to the S-layer (glyco-)proteins, sugar polymers like pseudomurein, methanochondroitin or heteropolysaccharides are also found in Archaeal Cell walls. These polymeric Cell wall structures can either form the sole Cell wall structure or be supported by an additional S-layer cover. A few Archaeal species even completely lack a Cell wall. Key Concepts: Archaeal Cell envelopes lack murein or a lipopolysaccharide (LPS)-containing outer membrane. Most Archaea posses a glycosylated proteinaceous surface layer (S-layer) as their sole Cell wall structure. In some Archaea, the Cell wall is composed of glycan polymers, like glutaminylglycan, heterosaccharide, methanochondroitin or pseudomurein. Keywords: archaea; Cell envelope; glutaminylglycan; glycosylation; heteropolysaccharide; methanochondroitin; pseudomurein; S-layer (glyco-)protein

  • The Archaeal Cell envelope
    Nature Reviews Microbiology, 2011
    Co-Authors: Sonja-verena Albers, Benjamin H. Meyer
    Abstract:

    At first glance, archaea and bacteria look alike; however, the composition of the Archaeal Cell envelope is fundamentally different from the bacterial Cell envelope. With just one exception, all archaea characterized to date have only a single membrane and most are covered by a paracrystalline protein layer. This Review discusses our current knowledge of the composition of the Archaeal Cell surface. We describe the wide range of Cell wall polymers, O- and N-glycosylated extraCellular proteins and other Cell surface structures that archaea use to interact with their environment.

Mechthild Pohlschroder - One of the best experts on this subject based on the ideXlab platform.

  • glycoproteomics of haloferax volcanii reveals an extensive glycoproteome and concurrence of different n glycosylation pathways
    bioRxiv, 2021
    Co-Authors: Stefan Schulze, Friedhelm Pfeiffer, Benjamin A Garcia, Mechthild Pohlschroder
    Abstract:

    Glycosylation is one of the most complex post-translational protein modifications. Its importance has been established not only for eukaryotes but also for a variety of prokaryotic Cellular processes, such as biofilm formation, motility and mating. However, comprehensive glycoproteomic analyses are largely missing in prokaryotes. Here we extend the phenotypic characterisation of N-glycosylation pathway mutants in Haloferax volcanii and provide a detailed glycoproteome for this model archaeon through the mass spectrometric analysis of intact glycopeptides. Using in-depth glycoproteomic datasets generated for the wild-type and mutant strains as well as a reanalysis of datasets within the Archaeal Proteome Project, we identify the largest Archaeal glycoproteome described so far. We further show that different N-glycosylation pathways can modify the same glycosites under the same culture conditions. The extent and complexity of the Hfx. volcanii N-glycoproteome revealed here provides new insights into the roles of N-glycosylation in Archaeal Cell biology.

  • Improved growth and morphological plasticity of Haloferax volcanii
    2020
    Co-Authors: Roshali T. De Silva, Mohd Farid Abdul-halim, Dorothea A. Pittrich, Hannah J. Brown, Mechthild Pohlschroder, Iain G. Duggin
    Abstract:

    Abstract Some microbes display pleomorphism, showing variable Cell shapes in a single culture, whereas others differentiate to adapt to changed environmental conditions. The pleomorphic archaeon Haloferax volcanii commonly forms discoid-shaped (‘plate’) Cells in culture, but may also be present as rods, and can develop into motile rods in soft agar, or longer filaments in certain biofilms. Here we report improvement of H. volcanii growth in both semi-defined and complex media by supplementing with eight trace-element micronutrients. With these supplemented media, transient development of plate Cells into uniformly-shaped rods was clearly observed during the early log phase of growth; Cells then reverted to plates for the late log and stationary phases. In media prepared with high-purity reagents, without supplemental trace elements, rods and other complex elongated morphologies (‘pleomorphic rods’) were observed at all growth stages of the culture; the highly-elongated Cells sometimes displayed a substantial tubule at one or less frequently both poles, as well as unusual tapered and highly-curved forms. Polar tubules were observed forming by initial mid-Cell narrowing or tubulation, causing a dumbbell-like shape, followed by Cell division towards one end. Formation of the uniform early-log rods, as well as the pleomorphic rods and tubules were dependent on the function of the tubulin-like cytoskeletal protein, CetZ1. Our results have revealed the remarkable morphological plasticity of H. volcanii, and shown that its changes in Cell shape occur in response to multiple signals. Importance Microbes can show morphological responses to changed environmental conditions, which are important for their survival in a wide variety of environments. These conditions and the specific role of such morphological changes are poorly defined. Here we describe improved growth media for the model archaeon Haloferax volcanii, and the identification and characterization of environmental conditions— micronutrient starvation and culture dilution—that induce striking morphological responses. We show that the morphological changes require the tubulin-like cytoskeletal protein, CetZ1. We expect the discovery of these responses and the application of these conditions to facilitate the use of this species in ongoing studies of Archaeal Cell biology.

  • Lipid Anchoring of Archaeosortase Substrates and MidCell Growth in Haloarchaea
    'American Society for Microbiology', 2020
    Co-Authors: Mohd Farid Abdul-halim, Friedhelm Pfeiffer, Stefan Schulze, Anthony Dilucido, Alexandre Wilson Bisson Filho, Mechthild Pohlschroder
    Abstract:

    The subCellular organization of biochemical processes in space and time is still one of the most mysterious topics in Archaeal Cell biology. Despite the fact that haloarchaea largely rely on covalent lipid anchoring to coat the Cell envelope, little is known about how Cells coordinate de novo synthesis and about the insertion of this proteinaceous layer throughout the Cell cycle. Here, we report the identification of two novel contributors to ArtA-dependent lipid-mediated protein anchoring to the Cell surface, HvPssA and HvPssD. ArtA, HvPssA, and HvPssD, as well as SLG, showed midCell localization during growth and cytokinesis, indicating that haloArchaeal Cells confine phospholipid processing in order to promote midCell elongation. Our findings have important implications for the biogenesis of the Cell surface.The Archaeal cytoplasmic membrane provides an anchor for many surface proteins. Recently, a novel membrane anchoring mechanism involving a peptidase, archaeosortase A (ArtA), and C-terminal lipid attachment of surface proteins was identified in the model archaeon Haloferax volcanii. ArtA is required for optimal Cell growth and morphogenesis, and the S-layer glycoprotein (SLG), the sole component of the H. volcanii Cell wall, is one of the targets for this anchoring mechanism. However, how exactly ArtA function and regulation control Cell growth and morphogenesis is still elusive. Here, we report that Archaeal homologs to the bacterial phosphatidylserine synthase (PssA) and phosphatidylserine decarboxylase (PssD) are involved in ArtA-dependent protein maturation. Haloferax volcanii strains lacking either HvPssA or HvPssD exhibited motility, growth, and morphological phenotypes similar to those of an ΔartA mutant. Moreover, we showed a loss of covalent lipid attachment to SLG in the ΔhvpssA mutant and that proteolytic cleavage of the ArtA substrate HVO_0405 was blocked in the ΔhvpssA and ΔhvpssD mutant strains. Strikingly, ArtA, HvPssA, and HvPssD green fluorescent protein (GFP) fusions colocalized to the midCell position of H. volcanii Cells, strongly supporting that they are involved in the same pathway. Finally, we have shown that the SLG is also recruited to the midCell before being secreted and lipid anchored at the Cell outer surface. Collectively, our data suggest that haloarchaea use the midCell as the main surface processing hot spot for Cell elongation, division, and shape determination

  • Archaeal Cell surface biogenesis
    Fems Microbiology Reviews, 2018
    Co-Authors: Mechthild Pohlschroder, Friedhelm Pfeiffer, Stefan Schulze, Mohd Farid Abdul Halim
    Abstract:

    Cell surfaces are critical for diverse functions across all domains of life, from Cell-Cell communication and nutrient uptake to Cell stability and surface attachment. While certain aspects of the mechanisms supporting the biosynthesis of the Archaeal Cell surface are unique, likely due to important differences in Cell surface compositions between domains, others are shared with bacteria or eukaryotes or both. Based on recent studies completed on a phylogenetically diverse array of archaea, from a wide variety of habitats, here we discuss advances in the characterization of mechanisms underpinning Archaeal Cell surface biogenesis. These include those facilitating co- and post-translational protein targeting to the Cell surface, transport into and across the Archaeal lipid membrane, and protein anchoring strategies. We also discuss, in some detail, the assembly of specific Cell surface structures, such as the Archaeal S-layer and the type IV pili. We will highlight the importance of post-translational protein modifications, such as lipid attachment and glycosylation, in the biosynthesis as well as the regulation of the functions of these Cell surface structures and present the differences and similarities in the biogenesis of type IV pili across prokaryotic domains.

  • permuting the pgf signature motif blocks both archaeosortase dependent c terminal cleavage and prenyl lipid attachment for the haloferax volcanii s layer glycoprotein
    Journal of Bacteriology, 2016
    Co-Authors: Mohd Farid Abdul Halim, Kelly R Karch, Yitian Zhou, Daniel H Haft, Benjamin A Garcia, Mechthild Pohlschroder
    Abstract:

    UNLABELLED For years, the S-layer glycoprotein (SLG), the sole component of many Archaeal Cell walls, was thought to be anchored to the Cell surface by a C-terminal transmembrane segment. Recently, however, we demonstrated that the Haloferax volcanii SLG C terminus is removed by an archaeosortase (ArtA), a novel peptidase. SLG, which was previously shown to be lipid modified, contains a C-terminal tripartite structure, including a highly conserved proline-glycine-phenylalanine (PGF) motif. Here, we demonstrate that ArtA does not process an SLG variant where the PGF motif is replaced with a PFG motif (slg(G796F,F797G)). Furthermore, using radiolabeling, we show that SLG lipid modification requires the PGF motif and is ArtA dependent, lending confirmation to the use of a novel C-terminal lipid-mediated protein-anchoring mechanism by prokaryotes. Similar to the case for the ΔartA strain, the growth, Cellular morphology, and Cell wall of the slg(G796F,F797G) strain, in which modifications of additional H. volcanii ArtA substrates should not be altered, are adversely affected, demonstrating the importance of these posttranslational SLG modifications. Our data suggest that ArtA is either directly or indirectly involved in a novel proteolysis-coupled, covalent lipid-mediated anchoring mechanism. Given that archaeosortase homologs are encoded by a broad range of prokaryotes, it is likely that this anchoring mechanism is widely conserved. IMPORTANCE Prokaryotic proteins bound to Cell surfaces through intercalation, covalent attachment, or protein-protein interactions play critical roles in essential Cellular processes. Unfortunately, the molecular mechanisms that anchor proteins to Archaeal Cell surfaces remain poorly characterized. Here, using the archaeon H. volcanii as a model system, we report the first in vivo studies of a novel protein-anchoring pathway involving lipid modification of a peptidase-processed C terminus. Our findings not only yield important insights into poorly understood aspects of Archaeal biology but also have important implications for key bacterial species, including those of the human microbiome. Additionally, insights may facilitate industrial applications, given that photosynthetic cyanobacteria encode uncharacterized homologs of this evolutionarily conserved enzyme, or may spur development of unique drug delivery systems.

Andreas Klingl - One of the best experts on this subject based on the ideXlab platform.

  • Archaeal Cell Walls.
    Sub-cellular biochemistry, 2019
    Co-Authors: Andreas Klingl, Carolin Pickl, Jennifer Flechsler
    Abstract:

    The Cell wall of archaea, as of any other prokaryote, is surrounding the Cell outside the cytoplasmic membrane and is mediating the interaction with the environment. In this regard, it can be involved in Cell shape maintenance, protection against virus, heat, acidity or alkalinity. Throughout the formation of pore like structures, it can resemble a micro sieve and thereby enable or disable transport processes. In some cases, Cell wall components can make up more than 10% of the whole Cellular protein. So far, a great variety of different Cell envelope structures and compounds have be found and described in detail. From all Archaeal Cell walls described so far, the most common structure is the S-layer. Other Archaeal Cell wall structures are pseudomurein, methanochondroitin, glutaminylglycan, sulfated heteropolysaccharides and protein sheaths and they are sometimes associated with additional proteins and protein complexes like the STABLE protease or the bindosome. Recent advances in electron microscopy also illustrated the presence of an outer(most) Cellular membrane within several Archaeal groups, comparable to the Gram-negative Cell wall within bacteria. Each new Cell wall structure that can be investigated in detail and that can be assigned with a specific function helps us to understand, how the earliest Cells on earth might have looked like.

  • S-layer and cytoplasmic membrane - exceptions from the typical Archaeal Cell wall with a focus on double membranes.
    Frontiers in microbiology, 2014
    Co-Authors: Andreas Klingl
    Abstract:

    The common idea of typical Cell wall architecture in archaea consists of a pseudo-crystalline proteinaceous surface layer (S-layer), situated upon the cytoplasmic membrane. This is true for the majority of described archaea, hitherto. Within the crenarchaea, the S-layer often represents the only Cell wall component, but there are various exceptions from this wall architecture. Beside (glycosylated) S-layers in (hyper)thermophilic cren- and euryarchaea as well as halophilic archaea, one can find a great variety of other Cell wall structures like proteoglycan-like S-layers (Halobacteria), glutaminylglycan (Natronococci), methanochondroitin (Methanosarcina) or double layered Cell walls with pseudomurein (Methanothermus and Methanopyrus). The presence of an outermost Cellular membrane in the crenArchaeal species Ignicoccus hospitalis already gave indications for an outer membrane similar to Gram-negative bacteria. Although there is just limited data concerning their biochemistry and ultrastructure, recent studies on the euryArchaeal methanogen Methanomassiliicoccus luminyensis, Cells of the ARMAN group, and the SM1 euryarchaeon delivered further examples for this exceptional Cell envelope type consisting of two membranes.

Reinhard Rachel - One of the best experts on this subject based on the ideXlab platform.

  • The Iho670 Fibers of Ignicoccus hospitalis: a New Type of Archaeal Cell Surface Appendage
    Journal of bacteriology, 2009
    Co-Authors: Daniel W. Müller, Reinhard Rachel, Reinhard Wirth, Carolin Meyer, Sonja Gürster, Ulf Küper, Gerhard Wanner, Annett Bellack
    Abstract:

    Ignicoccus hospitalis forms many Cell surface appendages, the Iho670 fibers (width, 14 nm; length, up to 20 mum), which constitute up to 5% of Cellular protein. They are composed mainly of protein Iho670, possessing no homology to Archaeal flagellins or fimbrins. Their existence as structures different from Archaeal flagella or fimbriae have gone unnoticed up to now because they are very brittle.

  • the unique structure of Archaeal hami highly complex Cell appendages with nano grappling hooks
    Molecular Microbiology, 2005
    Co-Authors: Christine Moissl, Reinhard Rachel, Ariane Briegel, Harald Engelhardt, Robert Huber
    Abstract:

    Proteinaceous, hair-like appendages known as fimbriae or pili commonly extend from the surface of prokaryotic Cells and serve important functions such as Cell adhesion, biofilm formation, motility and DNA transfer. Here we show that a novel group of archaea from cold, sulphidic springs has developed Cell surface appendages of an unexpectedly high complexity with a well-defined base-to-top organization. It represents a new class of filamentous Cell appendages, for which the term 'hamus' is proposed. Each Archaeal Cell is surrounded by a halo of about 100 hami, which mediate strong adhesion of the Cells to surfaces of different chemical composition. The hami are mainly composed of 120 kDa subunits and remained stable in a broad temperature and pH range (0-70 degrees C; 0.5-11.5). Electron microscopy and cryo-electron tomography revealed that the hamus filament possesses a helical basic structure. At periodic distances, three prickles emanate from the filament, giving it the character of industrially produced barbwire. At its distal end the hami carry a tripartite, barbed grappling hook (60 nm in diameter). The architecture of this molecular hook is reminiscent of man-made fishhooks, grapples and anchors. It appears that nature has developed a perfect mechanical nano-tool in the course of biological evolution, which also might prove useful in the field of nanobiotechnology.

  • in situ growth of the novel sm1 euryarchaeon from a string of pearls like microbial community in its cold biotope its physical separation and insights into its structure and physiology
    Archives of Microbiology, 2003
    Co-Authors: Christine Moissl, Reinhard Rachel, Christian Rudolph, Marcus Koch, Robert Huber
    Abstract:

    Recently, a unique Archaeal/bacterial community that grows in a macroscopically visible string-of-pearls-like structure in cold (~10 degrees C), sulfurous marsh water was discovered. Here, a new technique is described that allows the fast and reliable growth of these string-of-pearls-like microbial communities in larger quantities on polyethylene nets in nature. The microbial net population, estimated to consist of about 10,000 single pearls, can be harvested once a week and the Archaeal Cells selectively separated by density gradient centrifugation. As in native pearls, the Archaeal Cell fraction obtained consisted of a single type of coccoid Cells only, 0.6 micro m in diameter. This novel type of euryarchaea has been tentatively named SM1 euryarchaeon. Electron microscopy and immuno-fluorescence in situ hybridization (immuno-FISH) revealed that about 100 pili-like fibers, up to 3 micro m in length, emanate radially from the surface of each Cell. The SM1 euryArchaeal Cells exhibited a viability of about 90%. The optimal conditions for viability were temperatures between -2 degrees C and 20 degrees C, pH 5-9, and low salt conditions; Cell viability was independent of oxygen partial pressures. The cultures stained gram-positive, the Cell wall was sensitive to SDS, EDTA and Proteinase K treatment. The Cells did not exhibit the typical fluorescence for methanogens and did not contain coenzyme F(420). The G+C-content was 34.5 mol%.

  • in situ growth of the novel sm1 euryarchaeon from a string of pearls like microbial community in its cold biotope its physical separation and insights into its structure and physiology
    Archives of Microbiology, 2003
    Co-Authors: Christine Moissl, Reinhard Rachel, Christian Rudolph, Marcus Koch, Robert Huber
    Abstract:

    Recently, a unique Archaeal/bacterial community that grows in a macroscopically visible string-of-pearls-like structure in cold (~10 °C), sulfurous marsh water was discovered. Here, a new technique is described that allows the fast and reliable growth of these string-of-pearls-like microbial communities in larger quantities on polyethylene nets in nature. The microbial net population, estimated to consist of about 10,000 single pearls, can be harvested once a week and the Archaeal Cells selectively separated by density gradient centrifugation. As in native pearls, the Archaeal Cell fraction obtained consisted of a single type of coccoid Cells only, 0.6 µm in diameter. This novel type of euryarchaea has been tentatively named SM1 euryarchaeon. Electron microscopy and immuno-fluorescence in situ hybridization (immuno-FISH) revealed that about 100 pili-like fibers, up to 3 µm in length, emanate radially from the surface of each Cell. The SM1 euryArchaeal Cells exhibited a viability of about 90%. The optimal conditions for viability were temperatures between −2 °C and 20 °C, pH 5–9, and low salt conditions; Cell viability was independent of oxygen partial pressures. The cultures stained gram-positive, the Cell wall was sensitive to SDS, EDTA and Proteinase K treatment. The Cells did not exhibit the typical fluorescence for methanogens and did not contain coenzyme F420. The G+C-content was 34.5 mol%.

Yosuke Koga - One of the best experts on this subject based on the ideXlab platform.