scholarly journals Identification of Genes Required for Synthesis of the Adhesive Holdfast in Caulobacter crescentus

2003 ◽  
Vol 185 (4) ◽  
pp. 1432-1442 ◽  
Author(s):  
Chris S. Smith ◽  
Aaron Hinz ◽  
Diane Bodenmiller ◽  
David E. Larson ◽  
Yves V. Brun
Keyword(s):  
Outer Membrane ◽  
Gene Cluster ◽  
Xanthomonas Campestris ◽  
Caulobacter Crescentus ◽  
Sequence Similarity ◽  
Gram Negative ◽  
Transmission Electron ◽  
Polar Development ◽  
Transposon Insertions ◽  
Polar Organelle

ABSTRACT Adhesion to both abiotic and biotic surfaces by the gram-negative prothescate bacterium Caulobacter crescentus is mediated by a polar organelle called the “holdfast,” which enables the bacterium to form stable monolayer biofilms. The holdfast, a complex polysaccharide composed in part of N-acetylglucosamine, localizes to the tip of the stalk (a thin cylindrical extension of the cell wall and membranes). We report here the isolation of adhesion mutants with transposon insertions in an uncharacterized gene cluster involved in holdfast biogenesis (hfs) as well as in previously identified polar development genes (podJ and pleC), and the holdfast attachment genes (hfa). Clean deletions of three of the four genes in the hfs gene cluster (hfsDAB) resulted in a severe holdfast biogenesis phenotype. These mutants do not bind to surfaces or to a fluorescently labeled lectin, specific for N-acetylglucosamine. Transmission electron microscopy indicated that the hfsDAB mutants fail to synthesize a holdfast at the stalk tip. The predicted hfs gene products have significant sequence similarity to proteins necessary for exopolysaccharide export in gram-negative bacteria. HfsA has sequence similarity to GumC from Xanthomonas campestris, which is involved in exopolysaccharide export in the periplasm. HfsD has sequence similarity to Wza from Escherichia coli, an outer membrane protein involved in secretion of polysaccharide through the outer membrane. HfsB is a novel protein involved in holdfast biogenesis. These data suggest that the hfs genes play an important role in holdfast export.

scholarly journals Click-correlative light and electron microscopy (click-AT-CLEM) for imaging and tracking azido-functionalized sphingolipids in bacteria

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Simon Peters ◽  
Lena Kaiser ◽  
Julian Fink ◽  
Fabian Schumacher ◽  
Veronika Perschin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Antimicrobial Activity ◽  
Outer Membrane ◽  
Light And Electron Microscopy ◽  
Super Resolution ◽  
Hydroxyl Group ◽  
Side Chain ◽  
Gram Negative ◽  
Array Tomography ◽  
Transmission Electron

AbstractSphingolipids, including ceramides, are a diverse group of structurally related lipids composed of a sphingoid base backbone coupled to a fatty acid side chain and modified terminal hydroxyl group. Recently, it has been shown that sphingolipids show antimicrobial activity against a broad range of pathogenic microorganisms. The antimicrobial mechanism, however, remains so far elusive. Here, we introduce ‘click-AT-CLEM’, a labeling technique for correlated light and electron microscopy (CLEM) based on the super-resolution array tomography (srAT) approach and bio-orthogonal click chemistry for imaging of azido-tagged sphingolipids to directly visualize their interaction with the model Gram-negative bacterium Neisseria meningitidis at subcellular level. We observed ultrastructural damage of bacteria and disruption of the bacterial outer membrane induced by two azido-modified sphingolipids by scanning electron microscopy and transmission electron microscopy. Click-AT-CLEM imaging and mass spectrometry clearly revealed efficient incorporation of azido-tagged sphingolipids into the outer membrane of Gram-negative bacteria as underlying cause of their antimicrobial activity.

scholarly journals Complete Genome Sequence ofCaulobacter crescentusSiphophage Sansa

2015 ◽  
Vol 3 (5) ◽  
Author(s):  
Leonardo Vara ◽  
Ashley A. Kane ◽  
Jesse L. Cahill ◽  
Eric S. Rasche ◽  
Gabriel F. Kuty Everett
Keyword(s):  
Cell Differentiation ◽  
Genome Sequence ◽  
Complete Genome Sequence ◽  
Complete Genome ◽  
Caulobacter Crescentus ◽  
Sequence Similarity ◽  
Model Organism ◽  
Gram Negative ◽  
Icosahedral Capsid

Caulobacter crescentusis a Gram-negative dimorphic model organism used to study cell differentiation. Siphophage Sansa is a newly isolated siphophage with an icosahedral capsid that infectsC. crescentus. Sansa shares no sequence similarity to other phages deposited in GenBank. Here, we describe its genome sequence and general features.

scholarly journals Refinement of the Xanthomonas campestris pv. vesicatoria hrpD and hrpE Operon Structure

2007 ◽  
Vol 20 (5) ◽  
pp. 559-567 ◽  
Author(s):  
Ernst Weber ◽  
Carolin Berger ◽  
Ulla Bonas ◽  
Ralf Koebnik
Keyword(s):  
Gene Cluster ◽  
Hypersensitive Response ◽  
Xanthomonas Campestris ◽  
Transcriptional Start Site ◽  
Gene Clusters ◽  
Inducible Promoter ◽  
Transcriptional Unit ◽  
Operon Structure ◽  
The Right ◽  
Transposon Insertions

The plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria possesses a type III secretion (T3S) system which is encoded in the 23-kb hypersensitive response and pathogenicity (hrp) gene cluster. The T3S system is essential for pathogenicity in susceptible hosts and the induction of the hypersensitive response in resistant plants. In this study, we revisited the operon structure of the right part of the hrp gene cluster. Based on complementation experiments of transposon insertions and reverse-transcription polymerase chain reaction analyses, the hrpD operon contains hrcQ, hrcR, hrcS, and hpaA, whereas hrcD, hrpD6, and hrpE belong to the hrpE operon. We determined the transcriptional start site of the hrpE operon and showed that there is a promoter upstream of hrcD containing a plant-inducible promoter box. Conserved secondary mRNA structures in the intergenic region between hrpD6 and hrpE suggest a posttranscriptional regulated expression of hrpE. Based on comparisons of different hrp gene clusters and the analysis of evolutionary rates, we propose that the hrpE transcriptional unit was integrated into the hrp gene cluster at a later time.

scholarly journals Relationships among the O-Antigen Gene Clusters ofSalmonella enterica Groups B, D1, D2, and D3

1998 ◽  
Vol 180 (4) ◽  
pp. 1002-1007 ◽  
Author(s):  
Heather Curd ◽  
Dan Liu ◽  
Peter R. Reeves
Keyword(s):  
Cell Wall ◽  
Gene Cluster ◽  
Salmonella Enterica ◽  
Sequence Similarity ◽  
Gene Clusters ◽  
Gram Negative Bacteria ◽  
Polymerase Gene ◽  
Gram Negative ◽  
Antigen Gene ◽  
O Antigen

ABSTRACT The O antigen is an important cell wall antigen of gram-negative bacteria, and the genes responsible for its biosynthesis are located in a gene cluster. We have cloned and sequenced the DNA segment unique to the O-antigen gene cluster of Salmonella enterica group D3. This segment includes a novel O-antigen polymerase gene (wzy D3). The polymerase gives α(1→6) linkages but has no detectable sequence similarity to that of group D2, which confers the same linkage. We find the remnant of a D3-likewzy gene in the O-antigen gene clusters of groups D1 and B and suggest that this is the original wzy gene of these O-antigen gene clusters.

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.

scholarly journals Hydrothermally Assisted Fabrication of TiO2-Fe3O4 Composite Materials and Their Antibacterial Activity

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4715
Author(s):  
Adam Kubiak ◽  
Marta Kubacka ◽  
Elżbieta Gabała ◽  
Anna Dobrowolska ◽  
Karol Synoradzki ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Composite Materials ◽  
Bet Surface Area ◽  
Molar Ratio ◽  
Oxide Content ◽  
Gram Positive ◽  
Gram Negative ◽  
Transmission Electron ◽  
Xrd Patterns ◽  
Oxide Composites

The TiO2-Fe3O4 composite materials were fabricated via the hydrothermal-assisted technique. It was determined how the molar ratio of TiO2 to Fe3O4 influences the crystalline structure and morphology of the synthesized composite materials. The effect of the molar ratio of components on the antibacterial activity was also analyzed. On the basis of XRD patterns for the obtained titanium(IV) oxide-iron(II, III) oxide composites, the two separate crystalline forms—anatase and magnetite —were observed. Transmission electron microscopy revealed particles of cubic and tetragonal shape for TiO2 and spherical for Fe3O4. The results of low-temperature nitrogen sorption analysis indicated that an increase in the iron(II, III) oxide content leads to a decrease in the BET surface area. Moreover, the superparamagnetic properties of titanium(IV) oxide-iron(II, III) oxide composites should be noted. An important aim of the work was to determine the antibacterial activity of selected TiO2-Fe3O4 materials. For this purpose, two representative strains of bacteria, the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, were used. The titanium(IV) oxide-iron(II, III) oxide composites demonstrated a large zone of growth inhibition for both Gram-positive and Gram-negative bacteria. Moreover, it was found that the analyzed materials can be reused as antibacterial agents in three consecutive cycles with good results.

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