Microsporidia Have a Peculiar Outer Membrane with Exterior Cytoplasmic Proteins

2021 ◽  
Author(s):  
Earl Weidner ◽  
Robin Overstreet
Keyword(s):  
Outer Membrane ◽  
Cytoplasmic Proteins

scholarly journals Amikacin and bacteriophage treatment modulates outer membrane proteins composition in Proteus mirabilis biofilm

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Agnieszka Maszewska ◽  
Magdalena Moryl ◽  
Junli Wu ◽  
Bin Liu ◽  
Lu Feng ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Proteus Mirabilis ◽  
Protein Biosynthesis ◽  
Outer Membrane Proteins ◽  
Wild Strain ◽  
Elongation Factor ◽  
Resistance Mechanisms ◽  
Trna Synthetases ◽  
Cytoplasmic Proteins

AbstractModification of outer membrane proteins (OMPs) is the first line of Gram-negative bacteria defence against antimicrobials. Here we point to Proteus mirabilis OMPs and their role in antibiotic and phage resistance. Protein profiles of amikacin (AMKrsv), phage (Brsv) and amikacin/phage (AMK/Brsv) resistant variants of P. mirabilis were compared to that obtained for a wild strain. In resistant variants there were identified 14, 1, 5 overexpressed and 13, 5, 1 downregulated proteins for AMKrsv, Brsv and AMK/Brsv, respectively. Application of phages with amikacin led to reducing the number of up- and downregulated proteins compared to single antibiotic treatment. Proteins isolated in AMKrsv are involved in protein biosynthesis, transcription and signal transduction, which correspond to well-known mechanisms of bacteria resistance to aminoglycosides. In isolated OMPs several cytoplasmic proteins, important in antibiotic resistance, were identified, probably as a result of environmental stress, e.g. elongation factor Tu, asparaginyl-tRNA and aspartyl-tRNA synthetases. In Brsv there were identified: NusA and dynamin superfamily protein which could play a role in bacteriophage resistance. In the resistant variants proteins associated with resistance mechanisms occurring in biofilm, e.g. polyphosphate kinase, flagella basal body rod protein were detected. These results indicate proteins important in the development of P. mirabilis antibiofilm therapies.

scholarly journals Effect of alkaline growth pH on the expression of cell envelope proteins in Fusobacterium nucleatum

Microbiology ◽  
2010 ◽  
Vol 156 (6) ◽  
pp. 1783-1794 ◽  
Author(s):  
Peter S. Zilm ◽  
Alex Mira ◽  
Christopher J. Bagley ◽  
Anthony H. Rogers
Keyword(s):  
Outer Membrane ◽  
Cell Envelope ◽  
Periodontal Diseases ◽  
Outer Membrane Proteins ◽  
Fusobacterium Nucleatum ◽  
Oral Bacteria ◽  
Envelope Proteins ◽  
Altered Expression ◽  
Cytoplasmic Proteins ◽  
Growth Ph

Fusobacterium nucleatum is a Gram-negative anaerobic organism that plays a central role in the development of periodontal diseases. The progression of periodontitis is associated with a rise in pH of the gingival sulcus which promotes the growth and expression of virulence factors by periodontopathic bacteria. We have previously reported that the expression of specific cytoplasmic proteins is altered by a shift in growth pH. In the present study we have compared cell envelope protein expression of F. nucleatum during chemostat growth at pH 7.2 and 7.8. From a total of 176 proteins resolved from the cell envelope, 15 were found to have altered expression in response to an increase in growth pH and were identified by MS. Upregulated proteins included an outer membrane porin which has been identified as playing a role in virulence, a periplasmic chaperone which assists in the folding of outer membrane proteins, and a transporter thought to be involved with iron uptake. Proteins downregulated at pH 7.8 were consistent with our previous findings that the bacterium reduces its catabolism of energy-yielding substrates in favour of energy-storage pathways. Among the downregulated proteins, two transporters which are involved in the uptake of C4 dicarboxylates and phosphate were identified. A putative protease and an enzyme associated with the metabolism of glutamate were also identified. A high proportion of the cell envelope proteins suggested by these data to play a role in the organism's response to alkaline growth pH may have arisen by lateral gene transfer. This would support the hypothesis that genes that provide an ability to adapt to the changing conditions of the oral environment may be readily shared between oral bacteria.

Molecular Structure of the Outermost Cell Wall Component of Spirillum Serpens

1977 ◽  
Vol 35 ◽  
pp. 342-343
Author(s):  
Wah Chiu ◽  
David Grano
Keyword(s):  
Molecular Structure ◽  
Cell Wall ◽  
Outer Membrane ◽  
Gel Electrophoresis ◽  
Electron Microscopic Examination ◽  
Electron Microscopic ◽  
Cell Wall Component ◽  
Protein Components ◽  
Exposure Technique ◽  
Structural Aspects

The periodic structure external to the outer membrane of Spirillum serpens VHA has been isolated by similar procedures to those used by Buckmire and Murray (1). From SDS gel electrophoresis, we have found that the isolated fragments contain several protein components, and that the crystalline structure is composed of a glycoprotein component with a molecular weight of ∽ 140,000 daltons (2). Under an electron microscopic examination, we have visualized the hexagonally-packed glycoprotein subunits, as well as the bilayer profile of the outer membrane. In this paper, we will discuss some structural aspects of the crystalline glycoproteins, based on computer-reconstructed images of the external cell wall fragments.The specimens were prepared for electron microscopy in two ways: negatively stained with 1% PTA, and maintained in a frozen-hydrated state (3). The micrographs were taken with a JEM-100B electron microscope with a field emission gun. The minimum exposure technique was essential for imaging the frozen- hydrated specimens.

Cryo-Electron Microscopy and Correlation Averaging of Frozen-Hydrated, Polymorphic 2D Crystals of the Mitochondrial Outer Membrane Channel

1990 ◽  
Vol 48 (1) ◽  
pp. 100-101
Author(s):  
Xiao-Wei Guo
Keyword(s):  
Outer Membrane ◽  
Hexagonal Lattice ◽  
Mitochondrial Outer Membrane ◽  
Rectangular Lattice ◽  
Electron Microscopic ◽  
Cryo Electron Microscopy ◽  
Voltage Dependent ◽  
Outer Membrane Channel ◽  
2D Crystals ◽  
Vdac Channel

Voltage-dependent, anion-selective channels (VDAC) are formed in the mitochondrial outer membrane (mitOM) by a 30-kDa polypeptide. These channels form ordered 2D arrays when mitOMs from Neurospora crassa are treated with soluble phospholipase A2. We obtain low-dose electron microscopic images of unstained specimens of VDAC crystals preserved in vitreous ice, using a Philips EM420 equipped with a Gatan cryo-transfer stage. We then use correlation analysis to compute average projections of the channel crystals. The procedure involves Fourier-filtration of a region within a crystal field to obtain a preliminary average that is subsequently cross-correlated with the entire crystal. Subregions are windowed from the crystal image at coordinates of peaks in the cross-correlation function (CCF, see Figures 1 and 2) and summed to form averages (Figure 3).The VDAC channel forms several different types of crystalline arrays in mitOMs. The polymorph first observed during phospholipase treatment is a parallelogram array (a=13 run, b=11.5 run, θ==109°) containing 6 water-filled pores per unit cell. Figure 1 shows the CCF of a sub-field of such an “oblique” array used to compute the correlation average of Figure 3A. With increased phospholipase treatment, other polymorphs are observed, often co-existing within the same crystal. For example, two distinct (but closely related) types of lattices occur in the field corresponding to the CCF of Figure 2: a “contracted” version of the parallelogram lattice (a=13 run, b=10 run, θ=99°), and a near-rectangular lattice (a=8.5 run, b=5 nm). The pattern of maxima in this CCF suggests that a third, near-hexagonal lattice (a=4.5 nm) may also be present. The correlation averages of Figures 3B-D were computed from polycrystalline fields, using peak coordinates in regions of CCFs corresponding to each of the three lattice types.

Electrophysiological Characterization of Transport Across Outer Membrane Channels from Gram-Negative Bacteria in Their Native Environment

2019 ◽  
Author(s):  
Jiajun Wang ◽  
Rémi Terrasse ◽  
Jayesh Arun Bafna ◽  
Lorraine Benier ◽  
Mathias Winterhalter
Keyword(s):  
Outer Membrane ◽  
Lipid Membrane ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Multi Drug Resistance ◽  
Gram Negative Bacteria ◽  
Membrane Channels ◽  
Gram Negative ◽  
Electrophysiological Characterization

Multi-drug resistance in Gram-negative bacteria is often associated with low permeability of the outer membrane. To investigate the role of membrane channels in the uptake of antibiotics, we extract, purify and reconstitute them into artificial planar membranes. To avoid this time-consuming procedure, here we show a robust approach using fusion of native outer membrane vesicles (OMV) into planar lipid bilayer which moreover allows also to some extend the characterization of membrane protein channels in their native environment. Two major membrane channels from <i>Escherichia coli</i>, OmpF and OmpC, were overexpressed from the host and the corresponding OMVs were collected. Each OMV fusion revealed surprisingly single or only few channel activities. The asymmetry of the OMV´s translates after fusion into the lipid membrane with the LPS dominantly present at the side of OMV addition. Compared to conventional reconstitution methods, the channels fused from OMVs containing LPS have similar conductance but a much broader distribution. The addition of Enrofloxacin on the LPS side yields somewhat higher association (<i>k<sub>on</sub></i>) and lower dissociation (<i>k<sub>off</sub></i>) rates compared to LPS-free reconstitution. We conclude that using outer membrane vesicles is a fast and easy approach for functional and structural studies of membrane channels in the native membrane.

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