Bacterial outer membrane protein analysis by electrophoresis and microchip technology

Effect of Plasmonic Gold Nanoprisms on Biofilm Formation and Heat Shock Proteins Expression in Human Pathogenic Bacteria

Gold nanoparticles have gained interest in biomedical sciences in the areas of nano-diagnostics, bio-labeling, drug delivery, and bacterial infection. In this study, we examined, for the first time, the antibacterial and antibiofilm properties of plasmonic gold nanoprisms against human pathogenic bacteria using MIC and crystal violet. In addition, the expression level of GroEL/GroES heat shock proteins was also investigated by western blot. Gold nanoparticles were characterized by TEM and EDX, which showed equilateral triangular prisms with an average edge length of 150 nm. Antibacterial activity testing showed a great effect of AuNPs against pathogenic bacteria with MICs values ranging from 50 μg/mL to 100 μg/mL. Nanoparticles demonstrated strong biofilm inhibition action with a percentage of inhibition ranging from 40.44 to 82.43%. Western blot analysis revealed that GroEL was an AuNPs-inducible protein with an increase of up to 66.04%, but GroES was down-regulated with a reduction of up to 46.81%. Accordingly, plasmonic gold nanoprisms, could be a good candidate for antibiotics substitution in order to treat bacterial infections.

Effects of microwave (2.45 GHz) irradiation on some biological characters of Salmonella typhimurium

The present study was carried out to evaluate the effects of sub-lethal doses of microwave radiation on some biological characteristics in Salmonella typhimurium. The aim was to show the relationship between this treatment and the development of radiotolerance in this pathogen because there is a need for more information on physiological responses of pathogens to sub-lethal doses of microwave radiation. So, the bacterial strain was treated with a dose of 3600J (40-s exposure with power P=90 W) to cause cellular damage. The results have shown that the exposure of bacteria to microwaves resulted in a significant inhibition of cellular growth. This treatment has notably increased the effectiveness of the most tested antibiotics by the amelioration or the appearance of sensitivity in exposed bacteria. Gas chromatography (GC) analysis was performed to demonstrate the modification of the fatty acids (FA) composition. Results obtained have shown that this treatment had a significant effect on the FA content with an increase of unsaturated FA percentage. The acquisition of sensitivity to the sodium deoxycholate and the significant increase in the amount of extracellular proteins in exposed bacteria has confirmed the weakening of the bacterial membrane by microwaves. This study represents one of the few demonstrating the modifications on the bacterial membrane as a cellular response to survive the non-ionising radiation stress.

Identification of Outer Membrane Proteins Altered in Response to UVC-Radiation in Vibrio parahaemolyticus and Vibrio alginolyticus

Vibrio parahaemolyticus and V. alginolyticus, marine foodborne pathogens, were treated with UVC-radiation (240 J/m(2)) to evaluate alterations in their outer membrane protein profiles. Outer membrane protein patterns of UVC-irradiated bacteria were found altered when analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Altered proteins were identified by mass spectrometry (MS and MS/MS) and analysis revealed that OmpW, OmpA, Long-chain fatty acid transport protein, Outer membrane receptor protein, Putative uncharacterized protein VP0167, Maltoporin (lamB), Polar flagellin B/D, Agglutination protein Peptidoglycan-associated lipoprotein and MltA-interacting protein MipA were appeared, thereby they can be considered as UVC-stress proteins in some vibrios. In addition, expression of OmpK decreased to non-detectable level. Furthermore, we observed a decrease or an increase in the expression level of other outer membrane proteins.

A gel-free proteomic-based method for the characterization of Bordetella pertussis clinical isolates

Bordetella pertussis (Bp) is the etiologic agent of pertussis or whooping cough, a highly contagious respiratory disease occurring primarily in infants and young children. Although vaccine preventable, pertussis cases have increased over the years leading researchers to re-evaluate vaccine control strategies. Since bacterial outer membrane proteins, comprising the surfaceome, often play roles in pathogenesis and antibody-mediated immunity, three recent Bp circulating isolates were examined using proteomics to identify any potential changes in surface protein expression. Fractions enriched for outer membrane proteins were digested with trypsin and the peptides analyzed by nano liquid chromatography-electrospray ionization-mass spectrometry (nLC-ESI-MS), followed by database analysis to elucidate the surfaceomes of our three Bp isolates. Furthermore, a less labor intensive non-gel based antibody affinity capture technology in conjunction with MS was employed to assess each Bp strains' immunogenic outer membrane proteins. This novel technique is generally applicable allowing for the identification of immunogenic surface expressed proteins on pertussis and other pathogenic bacteria.

Identification of outer membrane proteins of Vibrio parahaemolyticus and Vibrio alginolyticus altered in response to γ-irradiation or long-term starvation

Vibrio parahaemolyticus and Vibrio alginolyticus were subjected to γ-irradiation (0.5 kGy) or starvation by incubation for 8 months in seawater to study modifications in their outer membrane protein patterns. After treatment, outer membrane protein profiles of starved or γ-irradiated bacteria were found to be altered when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Altered proteins were identified by mass spectrometry (MS and MS/MS) and analyses revealed that OmpU can be considered a starvation stress-induced protein. In addition, expression of OtnA, OmpW, OmpA and peptidoglycan-associated lipoprotein decreased to non-detectable levels in starved cells. Furthermore, MltA-interacting protein MipA appeared under γ-irradiation or starvation conditions. Thus, it can be considered to be a γ-irradiation, long-term starvation stress protein in some vibrios.

Quantitative analysis of cell surface membrane proteins using membrane-impermeable chemical probe coupled with 18O labeling

We report a mass spectrometry-based strategy for quantitative analysis of cell surface membrane proteome changes. The strategy includes enrichment of surface membrane proteins using a membrane-impermeable chemical probe followed by stable isotope (18)O labeling and LC-MS analysis. We applied this strategy for enriching membrane proteins expressed by Shewanella oneidensis MR-1, a Gram-negative bacterium with known metal-reduction capability via extracellular electron transfer between outer membrane proteins and extracellular electron receptors. LC/MS/MS analysis resulted in the identification of about 400 proteins with 79% of them being predicted to be membrane localized. Quantitative aspects of the membrane enrichment were shown by peptide level (16)O and (18)O labeling of proteins from wild-type and mutant cells (generated from deletion of a type II secretion protein, GspD) prior to LC-MS analysis. Using a chemical probe labeled pure protein as an internal standard for normalization, the quantitative data revealed reduced abundances in Delta gspD mutant cells of many outer membrane proteins including the outer membrane c-type cytochromes OmcA and MtrC, in agreement with a previous report that these proteins are substrates of the type II secretion system.

Alterations of outer membrane proteins and virulence genes expression in gamma-irradiated Vibrio parahaemolyticus and Vibrio alginolyticus

Gamma-irradiation technology sterilizes microorganisms and thereby prevents decay and improves the safety and shelf stability of food products. In this study we treated the foodborne pathogens Vibrio parahaemolyticus and Vibrio alginolyticus with gamma-irradiation (0.5 kGy) to evaluate their adaptative response. Outer membrane protein patterns of irradiated bacteria were found altered when analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. These modifications were manifested by the appearance and/or disappearance of bands as well as in the expression level of certain proteins. In addition, we searched for the presence of eight Vibrio cholerae virulence genes, toxR, toxS, toxRS, ctxA, zot, ace, toxT, and virulence pathogenicity island (VPI), in the genome of investigated strains. The expression of toxR, toxS, VPI, and ace genes in gamma-irradiated bacteria, studied by reverse transcriptase polymerase chain reaction, was altered. These variations were manifested by an increase and/or a decrease in the expression level of tested virulence genes.

Electrophoretic and electrochromatographic separation of proteins in capillaries: an update covering 2007-2009

This review article covers 3-year period from 2007 to 2009 and is a continuation of the review article by V. Dolnik, [Electrophoresis 2008, 29, 143-156]. This article with 125 references describes recent developments in CE and CEC of proteins in capillary format and does not cover the developments of CE and CEC in microchip format, since Tran et al. review the microchip subject in this special issue. The present review article has four major topics including (i) the separation media, (ii) multidimensional separations, (iii) detection, and (iv) applications.

Enzymatic, outer membrane proteins and plasmid alterations of starved Vibrio parahaemolyticus and Vibrio alginolyticus cells in seawater

The marine bacteria Vibrio parahaemolyticus and V. alginolyticus were incubated in seawater for 8 months to evaluate their adaptative responses to starvation. The starved cells showed an altered biochemical and enzymatic profiles, respectively, on Api 20E and Api ZYM systems and an evolution to the filterable minicells state capable to pass membrane pore size 0.45 microm. Outer membrane proteins patterns of stressed bacteria were also altered. Indeed, these modifications were manifested by the appearance and/or disappearance of bands as well as in the level of expression of certain proteins. Plasmids profiles analysis showed that V. alginolyticus ATCC 33787 lost three plasmids, whereas other tested strains conserved their initial profiles.

Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome

The bacterial cell-envelope consists of a complex arrangement of lipids, proteins and carbohydrates that serves as the interface between a microorganism and its environment or, with pathogens, a human host. Escherichia coli has long been investigated as a leading model system to elucidate the fundamental mechanisms underlying microbial cell-envelope biology. This includes extensive descriptions of the molecular identities, biochemical activities and evolutionary trajectories of integral transmembrane proteins, many of which play critical roles in infectious disease and antibiotic resistance. Strikingly, however, only half of the c. 1200 putative cell-envelope-related proteins of E. coli currently have experimentally attributed functions, indicating an opportunity for discovery. In this review, we summarize the state of the art of computational and proteomic approaches for determining the components of the E. coli cell-envelope proteome, as well as exploring the physical and functional interactions that underlie its biogenesis and functionality. We also provide a comprehensive comparative benchmarking analysis on the performance of different bioinformatic and proteomic methods commonly used to determine the subcellular localization of bacterial proteins.

Two-dimensional electrophoresis of membrane proteins

One third of all genes of various organisms encode membrane proteins, emphasizing their crucial cellular role. However, due to their high hydrophobicity, membrane proteins demonstrate low solubility and a high tendency for aggregation. Indeed, conventional two-dimensional gel electrophoresis (2-DE), a powerful electrophoretic method for the separation of complex protein samples that applies isoelectric focusing (IEF) in the first dimension and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in the second dimension, has a strong bias against membrane proteins. This review describes two-dimensional electrophoretic techniques that can be used to separate membrane proteins. Alternative methods for performing conventional 2-DE are highlighted; these involve replacing the IEF with electrophoresis using cationic detergents, namely 16-benzyldimethyl-n-hexadecylammonium chloride (16-BAC) and cetyl trimethyl ammonium bromide (CTAB), or the anionic detergent SDS. Finally, the separation of native membrane protein complexes through the application of blue and clear native gel electrophoresis (BN/CN-PAGE) is reviewed, as well as the free-flow electrophoresis (FFE) of membranes.