scholarly journals An Abnormally High Closing Potential of the OMPF Porin Channel from Yersinia Ruckeri: The Role of Charged Residues and Intramolecular Bonds

Acta Naturae ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 89-98
Author(s):  
D. K. Chistyulin ◽  
O. D. Novikova ◽  
E. A. Zelepuga ◽  
V. A. Khomenko ◽  
G. N. Likhatskaya ◽  
...  
Keyword(s):  
Lipid Membranes ◽  
Gram Negative Bacteria ◽  
Amino Acid Residues ◽  
Yersinia Ruckeri ◽  
Ompf Porin ◽  
E Coli ◽  
Total Conductance ◽  
Voltage Dependent ◽  
Acidic Conditions

Electrophysiological experiments on bilayer lipid membranes showed that the isolated outer membrane major porin of Yersinia ruckeri (YrOmpF) exhibits activity typical of porins from Gram-negative bacteria, forming channels with a mean conductance of 230 pS (in 0.1 M KCl) and slight asymmetry with respect to the applied voltage. Under acidic conditions (up to pH = 3.0), there was no significant decrease in the total conductance of the YrOmpF channel reconstituted into the bilayer. The studied channel significantly differed from the porins of other bacteria by high values of its critical closing potential (Vc): Vc = 232 mV at pH = 7.0 and Vc = 164 mV at pH = 5.0. A theoretical model of the YrOmpF spatial structure was used for the analysis of the charge distribution in the mouth and inside the channel to explain these properties and quantitatively assess the bonds between the amino acid residues in the L3 loop and on the inner wall of the barrel. The parameters of YrOmpF were compared with those of the classical OmpF porin from E. coli. The results of electrophysiological experiments and theoretical analysis are discussed in terms of the mechanism for voltage-dependent closing of porin channels.

SATP (YaaH), a succinate–acetate transporter protein in Escherichia coli

2013 ◽  
Vol 454 (3) ◽  
pp. 585-595 ◽  
Author(s):  
Joana Sá-Pessoa ◽  
Sandra Paiva ◽  
David Ribas ◽  
Inês Jesus Silva ◽  
Sandra Cristina Viegas ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Succinic Acid ◽  
Critical Role ◽  
Amino Acid Residues ◽  
E Coli ◽  
Transporter Protein ◽  
Affinity Constants ◽  
In Trans

In the present paper we describe a new carboxylic acid transporter in Escherichia coli encoded by the gene yaaH. In contrast to what had been described for other YaaH family members, the E. coli transporter is highly specific for acetic acid (a monocarboxylate) and for succinic acid (a dicarboxylate), with affinity constants at pH 6.0 of 1.24±0.13 mM for acetic acid and 1.18±0.10 mM for succinic acid. In glucose-grown cells the ΔyaaH mutant is compromised for the uptake of both labelled acetic and succinic acids. YaaH, together with ActP, described previously as an acetate transporter, affect the use of acetic acid as sole carbon and energy source. Both genes have to be deleted simultaneously to abolish acetate transport. The uptake of acetate and succinate was restored when yaaH was expressed in trans in ΔyaaH ΔactP cells. We also demonstrate the critical role of YaaH amino acid residues Leu131 and Ala164 on the enhanced ability to transport lactate. Owing to its functional role in acetate and succinate uptake we propose its assignment as SatP: the Succinate–Acetate Transporter Protein.

DNA methylation in Yersinia enterocolitica: role of the DNA adenine methyltransferase in mismatch repair and regulation of virulence factors

Microbiology ◽  
2005 ◽  
Vol 151 (7) ◽  
pp. 2291-2299 ◽  
Author(s):  
Stefan Fälker ◽  
M. Alexander Schmidt ◽  
Gerhard Heusipp
Keyword(s):  
Mismatch Repair ◽  
Yersinia Enterocolitica ◽  
Virulence Genes ◽  
Spontaneous Mutation ◽  
Gram Negative Bacteria ◽  
E Coli ◽  
Physiological Processes ◽  
Dna Adenine Methyltransferase

DNA adenine methyltransferase (Dam) plays an important role in physiological processes of Gram-negative bacteria such as mismatch repair and replication. In addition, Dam regulates the expression of virulence genes in various species. The authors cloned the dam gene of Yersinia enterocolitica and showed that Dam is essential for viability. Dam overproduction in Y. enterocolitica resulted in an increased frequency of spontaneous mutation and decreased resistance to 2-aminopurine; however, these effects were only marginal compared to the effect of overproduction of Escherichia coli-derived Dam in Y. enterocolitica, implying different roles or activities of Dam in mismatch repair of the two species. These differences in Dam function are not the cause for the essentiality of Dam in Y. enterocolitica, as Dam of E. coli can complement a dam defect in Y. enterocolitica. Instead, Dam seems to interfere with expression of essential genes. Furthermore, Dam mediates virulence of Y. enterocolitica. Dam overproduction results in increased tissue culture invasion of Y. enterocolitica, while the expression of specifically in vivo-expressed genes is not altered.

scholarly journals Binding From both sides: TolR and full-length OmpA bind and maintain the local structure of the E. coli cell wall

2018 ◽  
Author(s):  
Alister T. Boags ◽  
Firdaus Samsudin ◽  
Syma Khalid
Keyword(s):  
Cell Wall ◽  
Electrostatic Interactions ◽  
Cell Envelope ◽  
Binding Domain ◽  
Gram Negative Bacteria ◽  
Inner Membrane ◽  
E Coli ◽  
Non Covalent Interactions ◽  
Covalent Interactions

SUMMARYWe present a molecular modeling and simulation study of the of the E. coli cell envelope, with a particular focus on the role of TolR, a native protein of the E. coli inner membrane in interactions with the cell wall. TolR has been proposed to bind to peptidoglycan, but the only structure of this protein thus far is in a conformation in which the putative peptidoglycan binding domain is not accessible. We show that a model of the extended conformation of the protein in which this domain is exposed, binds peptidoglycan largely through electrostatic interactions. We show that non-covalent interactions of TolR and OmpA with the cell wall, from the inner membrane and outer membrane sides respectively, maintain the position of the cell wall even in the absence of Braun’s lipoprotein. When OmpA is truncated to remove the peptidoglycan binding domain, TolR is able to pull the cell wall down towards the inner membrane. The charged residues that mediate the cell-wall interactions of TolR in our simulations, are conserved across a number of species of Gram-negative bacteria.

scholarly journals TmSpz4 Plays an Important Role in Regulating the Production of Antimicrobial Peptides in Response to Escherichia coli and Candida albicans Infections

2020 ◽  
Vol 21 (5) ◽  
pp. 1878 ◽  
Author(s):  
Tariku Tesfaye Edosa ◽  
Yong Hun Jo ◽  
Maryam Keshavarz ◽  
Young Min Bae ◽  
Dong Hyun Kim ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Candida Albicans ◽  
Immune Responses ◽  
Fungal Infections ◽  
Larval Survival ◽  
Gram Negative Bacteria ◽  
Functional Importance ◽  
E Coli ◽  
Microbial Infections

Spätzle family proteins activate the Toll pathway and induce antimicrobial peptide (AMP) production against microbial infections. However, the functional importance of Tmspätzle4 (TmSpz4) in the immune response of Tenebrio molitor has not been reported. Therefore, here, we have identified and functionally characterized the role of TmSpz4 against bacterial and fungal infections. We showed that TmSpz4 expression was significantly induced in hemocytes at 6 h post-injection with Escherichia coli, Staphylococcus aureus, and Candida albicans. TmSpz4 knock-down significantly reduced larval survival against E. coli and C. albicans. To understand the reason for the survivability difference, the role of TmSpz4 in AMP production was examined in TmSpz4-silenced larvae following microbe injection. The AMPs that are active against Gram-negative bacteria, including TmTenecin-2, TmTenecin-4, TmAttacin-1a, TmDefensin-2, and TmCecropin-2, were significantly downregulated in response to E. coli in TmSpz4-silenced larvae. Similarly, the expression of TmTenecin-1, TmTenecin-3, TmThaumatin-like protein-1 and -2, TmDefensin-1, TmDefensin-2, and TmCecropin-2 were downregulated in response to C. albicans in TmSpz4-silenced larvae. In addition, the transcription factor NF-κB (TmDorX1 and TmDorX2) expression was significantly suppression in TmSpz4-silenced larvae. In conclusion, these results suggest that TmSpz4 plays a key role in regulating immune responses of T. molitor against to E. coli and C. albicans.

Escherichia coli tol and rcs genes participate in the complex network affecting curli synthesis

Microbiology ◽  
2005 ◽  
Vol 151 (7) ◽  
pp. 2487-2497 ◽  
Author(s):  
Anne Vianney ◽  
Grégory Jubelin ◽  
Sophie Renault ◽  
Corine Dorel ◽  
Philippe Lejeune ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Membrane Integrity ◽  
Regulatory Proteins ◽  
Gram Negative Bacteria ◽  
Dependent Manner ◽  
Dominant Effect ◽  
Gram Negative ◽  
E Coli

Curli are necessary for the adherence of Escherichia coli to surfaces, and to each other, during biofilm formation, and the csgBA and csgDEFG operons are both required for their synthesis. A recent survey of gene expression in Pseudomonas aeruginosa biofilms has identified tolA as a gene activated in biofilms. The tol genes play a fundamental role in maintaining the outer-membrane integrity of Gram-negative bacteria. RcsC, the sensor of the RcsBCD phosphorelay, is involved, together with RcsA, in colanic acid capsule synthesis, and also modulates the expression of tolQRA and csgDEFG. In addition, the RcsBCD phosphorelay is activated in tol mutants or when Tol proteins are overexpressed. These results led the authors to investigate the role of the tol genes in biofilm formation in laboratory and clinical isolates of E. coli. It was shown that the adherence of cells was lowered in the tol mutants. This could be the result of a drastic decrease in the expression of the csgBA operon, even though the expression of csgDEFG was slightly increased under such conditions. It was also shown that the Rcs system negatively controls the expression of the two csg operons in an RcsA-dependent manner. In the tol mutants, activation of csgDEFG occurred via OmpR and was dominant upon repression by RcsB and RcsA, while these two regulatory proteins repressed csgBA through a dominant effect on the activator protein CsgD, thus affecting curli synthesis. The results demonstrate that the Rcs system, previously known to control the synthesis of the capsule and the flagella, is an additional component involved in the regulation of curli. Furthermore, it is shown that the defect in cell motility observed in the tol mutants depends on RcsB and RcsA.

scholarly journals Dissemination of Carbapenem-resistance and Plasmids-encoding Carbapenemases in Gram-negative Bacteria Isolated from India

2020 ◽  
Author(s):  
Prasanth Manohar ◽  
Sebastian Leptihn ◽  
Bruno S. Lopes ◽  
Nachimuthu Ramesh
Keyword(s):  
Tamil Nadu ◽  
Treatment Options ◽  
Public Health Problem ◽  
Carbapenem Resistance ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli ◽  
Diagnostic Center ◽  
Lactamase Gene

AbstractCarbapenem resistance in Gram-negative bacteria is an ongoing public-health problem of global dimensions leaving very few treatment options for severely infected patients. This study focuses on the dissemination of plasmid-borne carbapenemase genes in Gram-negative bacteria in Tamil Nadu, India. A total of 151 non-repetitive isolates belonging to 11 genera were collected from a diagnostic center in Tamil Nadu. E. coli (n=57) isolates were classified as, Enteropathogenic (n=12), Enteroaggregative (n=9), Enterohemorrhagic (n=8), Enterotoxigenic (n=3), Enteroinvasive (n=1) and unclassified E. coli (n=24). Of the 45 Klebsiella species, 14 were K1 whereas 11 were K2 serotype and in 20 Klebsiella serotype could not be determined. Other isolates (n=49) consisted of P. aeruginosa, S. typhi, E. cloacae, A. baumannii, S. marcescens, A. xylosoxidans, P. mirabilis and E. meningoseptica. Of the 151 isolates, 71% (n=107) and 68% (n=103) were found to be resistant to meropenem and imipenem respectively. The most prevalent beta-lactamase gene was blaNDM-1 (21%, 12/57) followed by blaOXA-181 (16%, 9/57), blaGES-9 (n=8), blaOXA-23 (n=7), blaIMP-1 (n=3), blaGES-1 (n=11) and blaOXA-51 (n=9). The unusual presence of blaOXA-23 was seen in E. coli (n=4), and blaOXA-23 and blaOXA-51 (IncA/C) in K. pneumoniae (n=3). Plasmid incompatibility (inc/rep) typing results showed that the plasmids carrying resistance genes (n=11) belonged to IncX, IncA/C, IncFIA-FIB and IncFIIA groups. E. coli and K. pneumoniae were able to transfer plasmid-borne carbapenemase via conjugation. This study highlights the prevalence of carbapenem resistance and the acquisition of plasmid-borne carbapenemase genes in Gram-negative bacteria highlighting the role of plasmid transfer in disseminating resistance.

Voltage-dependent gating properties of the channel formed by E. coli hemolysin in planar lipid membranes

1989 ◽  
Vol 9 (4) ◽  
pp. 465-473 ◽  
Author(s):  
Gianfranco Menestrina ◽  
Monica Ropele
Keyword(s):  
Lipid Membranes ◽  
Ph Dependence ◽  
Phospholipid Bilayer ◽  
Bilayer Membranes ◽  
E Coli ◽  
Simple Physical Model ◽  
Voltage Dependent ◽  
Planar Lipid Membranes ◽  
Escherichia Coli Hemolysin ◽  
Gating Process

Escherichia coli hemolysin forms cation selective, ion-permeable channels of large conductance in planar phospholipid bilayer membranes. The pore formation mechanism is voltage dependent resembling that of some colicins and of diphtheria toxin: pores open when negative voltages are applied and close with positive potentials. The pH dependence of this gating process suggests that it is mediated by a negative fixed charge present in the lumen of the pore. A simple physical model of how the channel opens and closes in response to the applied voltage is given.

Graft-Versus-Host Disease Alters Intestinal Microbial Ecology by Inhibiting Production of Enteric Defensins

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 244-244
Author(s):  
Yoshihiro Eriguchi ◽  
Shuichiro Takashima ◽  
Noriko Miyake ◽  
Yoji Nagasaki ◽  
Nobuyuki Shimono ◽  
...  
Keyword(s):  
Paneth Cell ◽  
Intestinal Microbiome ◽  
Gram Negative Bacteria ◽  
Obligate Anaerobe ◽  
Gut Flora ◽  
Gram Negative ◽  
E Coli ◽  
Intestinal Gvhd ◽  
Intestinal Ecology

Abstract Abstract 244 Bacterial infection is a serious complication of bone marrow transplantation (BMT). Intestinal GVHD, in particular, significantly enhances the risk for Gram-negative septicemia. The majority of the intestinal microbiome of the hosts consists of non-cultivable obligate anaerobes, while the Gram-negative bacteria such as Escherichia coli (E. coli) make up a small proportion of the microflora. Thus, it remains unclear why Gram-negative septicemia is dominant in intestinal GVHD, while the role of systemic immunosuppression and use of antibiotics is well-appreciated. We evaluated gut flora changes in the course of GVHD in mouse models of BMT without giving antibiotic or immunosuppresive drugs. Lethally irradiated B6D2F1 (H-2b/d) or B6C3F1 (H-2b/k) mice were injected with 5 × 106 T-cell depleted BM alone (non-GVHD controls) or with 2 × 106 T cells (GVHD group) from MHC-mismatched B6 (H-2b) donors on day 0. Intestinal microflora was identified by using terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA gene libraries constructed from each sample of gut contents. It consisted of approximately 80% of obligate anaerobe, and 20% of anaerobe such as Lactobacilli and Clostridia with very few E. coli before BMT. After BMT, this diversity of gut flora was preserved in non-GVHD controls (Table). In contrast, GVHD mice showed a marked increase of E. coli with a significant decrease in the members of obligate anaerobe. This was associated with dissemination of E. coli to the mesenteric lymph nodes (mLNs) and liver, with elevated serum levels of lipopolysaccharide (LPS). Such a loss of diversity of gut flora with a flora shift towards E. coli was significantly associated with morbidity and mortality of GVHD. Numbers of T-RFLP peaks that indicate diversity of intestinal flora were inversely correlated with GVHD clinical scores (p<0.001). A degree of E. coli proportion has significant correlation with GVHD clinical scores (p<0.001) and GVHD mortality (80% in high E. coli group vs. 0% in low E. coli group). We then investigated the underlying mechanisms of the disruption of intestinal ecology in GVHD. Paneth cell derived α-defensins are essential regulators of intestinal microbial ecology. We therefore hypothesized that Paneth cell damage in GVHD inhibited production of enteric defensins and disrupted intestinal ecology. Immunohistochemistry for lysozyme that marks Paneth cells showed significant reduction of Paneth cells in GVHD and quantitative real-time PCR analysis showed dramatically reduced expression of enteric defensins including Defa21, Defa1, Defa4, Defa5, and Defcr-rs1 (Table). These results suggest that Paneth cell injury in GVHD could lead to lower expression of enteric defensins and a shift of gut flora from commensal microorganisms towards widespread prevelance of gram-negative bacteria in the intestinal microbiome, and the subsequent high risk for the development of life threatening Gram-negative septicemia. LPS derived from Gram-negative bacteria plays an important role in amplifying systemic GVHD. Thus, such an alteration of intestinal ecology may be related to exaggeration of systemic GVHD. These results thus uncover the previously unrecognized role of the intrinsic antimicrobial peptides and the crosstalk between hosts and the intestinal microbes in the pathogenesis of GVHD and infection after allogeneic BMT. Disclosures: No relevant conflicts of interest to declare.

scholarly journals How Bacteria Consume Their Own Exoskeletons (Turnover and Recycling of Cell Wall Peptidoglycan)

2008 ◽  
Vol 72 (2) ◽  
pp. 211-227 ◽  
Author(s):  
James T. Park ◽  
Tsuyoshi Uehara
Keyword(s):  
Energy Source ◽  
Degradation Products ◽  
Side Wall ◽  
Amino Sugars ◽  
Gram Negative Bacteria ◽  
Periplasmic Binding Protein ◽  
Gram Negative ◽  
E Coli ◽  
The Individual

SUMMARY The phenomenon of peptidoglycan recycling is reviewed. Gram-negative bacteria such as Escherichia coli break down and reuse over 60% of the peptidoglycan of their side wall each generation. Recycling of newly made peptidoglycan during septum synthesis occurs at an even faster rate. Nine enzymes, one permease, and one periplasmic binding protein in E. coli that appear to have as their sole function the recovery of degradation products from peptidoglycan, thereby making them available for the cell to resynthesize more peptidoglycan or to use as an energy source, have been identified. It is shown that all of the amino acids and amino sugars of peptidoglycan are recycled. The discovery and properties of the individual proteins and the pathways involved are presented. In addition, the possible role of various peptidoglycan degradation products in the induction of β-lactamase is discussed.

scholarly journals Sequential metabolic expressions of the lethal process in human serum-treated Escherichia coli: role of lysozyme

1980 ◽  
Vol 28 (3) ◽  
pp. 735-745
Author(s):  
R J Martinez ◽  
S F Carroll
Keyword(s):  
Escherichia Coli ◽  
Human Serum ◽  
Membrane Integrity ◽  
Response To Treatment ◽  
Gram Negative Bacteria ◽  
Human Lysozyme ◽  
E Coli ◽  
Normal Human ◽  
Hydrolysis Of

Several metabolic parameters indicative of Escherichia coli function and integrity were kinetically examined in response to treatment with normal human serum in the presence and absence of functional human lysozyme. Specific inhibition of this enzyme in bacteriolytic and bactericidal reactions was accomplished by using purified rabbit anti-human lysozyme immunoglobulin G. Initiation of the complement-mediated alterations of cytoplasmic membrane integrity, as judged by the leakage of 86Rb from prelabeled cells or the hydrolysis of o-nitrophenyl-beta-D-galactopyranoside by a cryptic strain, was found to be independent of lysozyme action. Furthermore, inhibition of macromolecular synthesis by E. coli in response to serum treatment occurred at the same time regardless of the functional state of lysozyme. Although the rate and extent of bacteriolysis were reduced in the absence of lysozyme, the bactericidal kinetics was unaffected. These results demonstrate that the lethal events associated with the action of antibody and complement on gram-negative bacteria are independent of lysozyme, suggesting an accessory role for this enzyme in immune reactions. A possible temporal sequence of complement-induced effects occurring at the cell surface is presented.

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