Iron Cycle Tuned by Outer-Membrane Cytochromes of Dissimilatory Metal-Reducing Bacteria: Interfacial Dynamics and Mechanisms In Vitro

2021 ◽  
Author(s):  
Sheng-Song Yu ◽  
Jie-Jie Chen ◽  
Rui-Fen Cheng ◽  
Yuan Min ◽  
Han-Qing Yu
Keyword(s):  
Outer Membrane ◽  
Interfacial Dynamics ◽  
Iron Cycle ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

On conducting electron traffic across the periplasm

2012 ◽  
Vol 40 (6) ◽  
pp. 1178-1180 ◽  
Author(s):  
Jeffrey A. Gralnick
Keyword(s):  
Physical Properties ◽  
Outer Membrane ◽  
Cytoplasmic Membrane ◽  
Respiratory Pathway ◽  
Redox Proteins ◽  
The Core ◽  
Core Components ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

Dissimilatory metal-reducing bacteria are able to conduct electrons from their cytoplasmic membrane across the periplasm and the outer membrane to redox proteins located on the surface of their cells. The Mtr respiratory pathway in Shewanella is the best-understood metal-reducing pathway to date. The core components of this pathway are well agreed upon, but are they sufficient? Could there be other components that we have yet to uncover? The present paper specifically considers the periplasm, its physical properties and organization. Two models are presented to explain how electrons could be conducted across this compartment in Shewanella.

Adaptive synthesis of a rough lipopolysaccharide in Geobacter sulfurreducens for metal reduction and detoxification

2021 ◽  
Author(s):  
Morgen M. Clark ◽  
Michael D. Paxhia ◽  
Jenna M. Young ◽  
Michael P. Manzella ◽  
Gemma Reguera
Keyword(s):  
Outer Membrane ◽  
Cell Envelope ◽  
Biological Significance ◽  
Geobacter Sulfurreducens ◽  
Metal Reduction ◽  
Permeability Barrier ◽  
O Antigen ◽  
Membrane Vesiculation ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

The ability of some metal-reducing bacteria to produce a rough (no O-antigen) lipopolysaccharide (LPS) could facilitate surface interactions with minerals and metal reduction. Consistent with this, the laboratory model metal reducer Geobacter sulfurreducens PCA produced two rough LPS isoforms (with or without a terminal methyl-quinovosamine sugar) when growing with the soluble electron acceptor, fumarate, but only expressed the shorter and more hydrophilic variant when reducing iron oxides. We reconstructed from genomic data conserved pathways for the synthesis of the rough LPS and generated heptosyltransferase mutants with partial (Δ rfaQ ) and complete (Δ rfaC ) truncations in the core oligosaccharide. The stepwise removal of the LPS core sugars reduced the hydrophilicity of the cell and increased outer membrane vesiculation. These changes in outer membrane charge and remodeling did not substantially impact planktonic growth but disrupted the developmental stages and structure of electroactive biofilms. Furthermore, the mutants assembled conductive pili for the extracellular mineralization of the toxic uranyl cation, yet were unable to prevent the permeation and mineralization of the radionuclide in the cell envelope. Hence, not only does the rough LPS promote cell-cell and cell-mineral interactions critical to biofilm formation and metal respiration, but it also functions as a permeability barrier to toxic metal cations. In doing so, the rough LPS maximizes the extracellular reduction of soluble and insoluble metals and preserves cell envelope functions critical to the environmental survival of Geobacter bacteria in metal rich environments and their performance in bioremediation and bioenergy applications. Importance Some metal-reducing bacteria produce a lipopolysaccharide (LPS) without the repeating sugars (O-antigen) that decorate the surface of most Gram-negative bacteria, but the biological significance of this adaptive feature has never been investigated. Using the model representative Geobacter sulfurreducens strain PCA and mutants carrying stepwise truncations in the LPS core sugars, we demonstrate the importance of the rough LPS in the control of cell surface chemistry during the respiration of iron minerals and the formation of electroactive biofilms. Importantly, we describe hitherto overlooked roles for the rough LPS in metal sequestration and outer membrane vesiculation that are critical for the extracellular reduction and detoxification of toxic metals and radionuclides. These results are of interest for the optimization of bioremediation schemes and electricity-harvesting platforms using these bacteria.

scholarly journals Assembly of an in vitro synthesized Escherichia coli outer membrane porin into its stable trimeric configuration.

1990 ◽  
Vol 265 (8) ◽  
pp. 4646-4651
Author(s):  
H de Cock ◽  
R Hendriks ◽  
T de Vrije ◽  
J Tommassen
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Outer Membrane Porin

scholarly journals Competitive Reduction of Pertechnetate (99TcO4−) by Dissimilatory Metal Reducing Bacteria and Biogenic Fe(II)

2011 ◽  
Vol 45 (3) ◽  
pp. 951-957 ◽  
Author(s):  
Andrew E. Plymale ◽  
James K. Fredrickson ◽  
John M. Zachara ◽  
Alice C. Dohnalkova ◽  
Steve M. Heald ◽  
...  
Keyword(s):  
Competitive Reduction ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

scholarly journals Exposure of ichnovirus particles to digitonin leads to enhanced infectivity and induces fusion from without in an in vitro model system

2007 ◽  
Vol 88 (11) ◽  
pp. 2977-2984 ◽  
Author(s):  
Don Stoltz ◽  
Renée Lapointe ◽  
Andrea Makkay ◽  
Michel Cusson
Keyword(s):  
Outer Membrane ◽  
In Vitro Model ◽  
Model System ◽  
Host Cells ◽  
Fusion Event ◽  
Susceptible Host ◽  
In Vitro Model System ◽  
Vitro Model

Unlike most viruses, the mature ichnovirus particle possesses two unit membrane envelopes. Following loss of the outer membrane in vivo, nucleocapsids are believed to gain entry into the cytosol via a membrane fusion event involving the inner membrane and the plasma membrane of susceptible host cells; accordingly, experimentally induced damage to the outer membrane might be expected to increase infectivity. Here, in an attempt to develop an in vitro model system for studying ichnovirus infection, we show that digitonin-induced disruption of the virion outer membrane not only increases infectivity, but also uncovers an activity not previously associated with any polydnavirus: fusion from without.

scholarly journals Mitochondrial Outer Membrane Proteins Assist Bid in Bax-mediated Lipidic Pore Formation

2009 ◽  
Vol 20 (8) ◽  
pp. 2276-2285 ◽  
Author(s):  
Blanca Schafer ◽  
Joel Quispe ◽  
Vineet Choudhary ◽  
Jerry E. Chipuk ◽  
Teddy G. Ajero ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Pore Formation ◽  
Outer Membrane Proteins ◽  
Mitochondrial Outer Membrane ◽  
Outer Membranes ◽  
Mitochondrial Outer Membrane Permeabilization ◽  
In Vitro Systems ◽  
Large Round ◽  
Key Features

Mitochondrial outer membrane permeabilization (MOMP) is a critical step in apoptosis and is regulated by Bcl-2 family proteins. In vitro systems using cardiolipin-containing liposomes have demonstrated the key features of MOMP induced by Bax and cleaved Bid; however, the nature of the “pores” and how they are formed remain obscure. We found that mitochondrial outer membranes contained very little cardiolipin, far less than that required for liposome permeabilization, despite their responsiveness to Bcl-2 family proteins. Strikingly, the incorporation of isolated mitochondrial outer membrane (MOM) proteins into liposomes lacking cardiolipin conferred responsiveness to cleaved Bid and Bax. Cardiolipin dependence was observed only when permeabilization was induced with cleaved Bid but not with Bid or Bim BH3 peptide or oligomerized Bax. Therefore, we conclude that MOM proteins specifically assist cleaved Bid in Bax-mediated permeabilization. Cryoelectron microscopy of cardiolipin-liposomes revealed that cleaved Bid and Bax produced large round holes with diameters of 25–100 nm, suggestive of lipidic pores. In sum, we propose that activated Bax induces lipidic pore formation and that MOM proteins assist cleaved Bid in this process in the absence of cardiolipin.

On mechanisms of colicin import: the outer membrane quandary

2018 ◽  
Vol 475 (23) ◽  
pp. 3903-3915 ◽  
Author(s):  
William A. Cramer ◽  
Onkar Sharma ◽  
S.D. Zakharov
Keyword(s):  
Outer Membrane ◽  
Catalytic Domain ◽  
Efflux Pump ◽  
Crystal Structure Analysis ◽  
Multidrug Efflux Pump ◽  
Terminal Domain ◽  
Colicin E1 ◽  
N Terminus ◽  
T Domain

Current problems in the understanding of colicin import across the Escherichia coli outer membrane (OM), involving a range of cytotoxic mechanisms, are discussed: (I) Crystal structure analysis of colicin E3 (RNAase) with bound OM vitamin B12 receptor, BtuB, and of the N-terminal translocation (T) domain of E3 and E9 (DNAase) inserted into the OM OmpF porin, provide details of the initial interaction of the colicin central receptor (R)- and N-terminal T-domain with OM receptors/translocators. (II) Features of the translocon include: (a) high-affinity (Kd ≈ 10−9 M) binding of the E3 receptor-binding R-domain E3 to BtuB; (b) insertion of disordered colicin N-terminal domain into the OmpF trimer; (c) binding of the N-terminus, documented for colicin E9, to the TolB protein on the periplasmic side of OmpF. Reinsertion of the colicin N-terminus into the second of the three pores in OmpF implies a colicin anchor site on the periplasmic side of OmpF. (III) Studies on the insertion of nuclease colicins into the cytoplasmic compartment imply that translocation proceeds via the C-terminal catalytic domain, proposed here to insert through the unoccupied third pore of the OmpF trimer, consistent with in vitro occlusion of OmpF channels by the isolated E3 C-terminal domain. (IV) Discussion of channel-forming colicins focuses mainly on colicin E1 for which BtuB is receptor and the OM TolC protein the proposed translocator. The ability of TolC, part of a multidrug efflux pump, for which there is no precedent for an import function, to provide a trans-periplasmic import pathway for colicin E1, is questioned on the basis of an unfavorable hairpin conformation of colicin N-terminal peptides inserted into TolC.

scholarly journals TheEscherichia coliβ-Barrel Assembly Machinery Is Sensitized to Perturbations under High Membrane Fluidity

2018 ◽  
Vol 201 (1) ◽  
Author(s):  
Kelly M. Storek ◽  
Rajesh Vij ◽  
Dawei Sun ◽  
Peter A. Smith ◽  
James T. Koerber ◽  
...  
Keyword(s):  
Amino Acid ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Membrane Fluidity ◽  
Amino Acid Substitutions ◽  
Inhibitory Antibody ◽  
Critical Determinant ◽  
Gram Negative ◽  
Growth Environment

ABSTRACTIntegral β-barrel membrane proteins are folded and inserted into the Gram-negative bacterial outer membrane by the β-barrel assembly machine (BAM). This essential complex, composed of a β-barrel protein, BamA, and four lipoproteins, BamB, BamC, BamD, and BamE, resides in the outer membrane, a unique asymmetrical lipid bilayer that is difficult to recapitulatein vitro. Thus, the probing of BAM function in living cells is critical to fully understand the mechanism of β-barrel folding. We recently identified an anti-BamA monoclonal antibody, MAB1, that is a specific and potent inhibitor of BamA function. Here, we show that the inhibitory effect of MAB1 is enhanced when BAM function is perturbed by either lowering the level of BamA or removing the nonessential BAM lipoproteins, BamB, BamC, or BamE. The disruption of BAM reduces BamA activity, increases outer membrane (OM) fluidity, and activates the σEstress response, suggesting the OM environment and BAM function are interconnected. Consistent with this idea, an increase in the membrane fluidity through changes in the growth environment or alterations to the lipopolysaccharide in the outer membrane is sufficient to provide resistance to MAB1 and enable the BAM to tolerate these perturbations. Amino acid substitutions in BamA at positions in the outer membrane spanning region or the periplasmic space remote from the extracellular MAB1 binding site also provide resistance to the inhibitory antibody. Our data highlight that the outer membrane environment is a critical determinant in the efficient and productive folding of β-barrel membrane proteins by BamA.IMPORTANCEBamA is an essential component of the β-barrel assembly machine (BAM) in the outer membranes of Gram-negative bacteria. We have used a recently described inhibitory anti-BamA antibody, MAB1, to identify the molecular requirements for BAM function. Resistance to this antibody can be achieved through changes to the outer membrane or by amino acid substitutions in BamA that allosterically affect the response to MAB1. Sensitivity to MAB1 is achieved by perturbing BAM function. By using MAB1 activity and functional assays as proxies for BAM function, we link outer membrane fluidity to BamA activity, demonstrating that an increase in membrane fluidity sensitizes the cells to BAM perturbations. Thus, the search for potential inhibitors of BamA function must consider the membrane environment in which β-barrel folding occurs.

In vitro study of virulence potential of Acinetobacter baumannii outer membrane vesicles

2017 ◽  
Vol 111 ◽  
pp. 218-224 ◽  
Author(s):  
Chandana Jha ◽  
Sujata Ghosh ◽  
Vikas Gautam ◽  
Pankaj Malhotra ◽  
Pallab Ray
Keyword(s):  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
In Vitro Study ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Vitro Study ◽  
Virulence Potential
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