Brianna Dalesandro

Related Articles

Combating bacterial infection by in situ self-assembly of AIEgen-peptide conjugate.

Biomaterials. 2020 Mar 14;244:119972

Authors: Yang C, Hu F, Zhang X, Ren C, Huang F, Liu J, Zhang Y, Yang L, Gao Y, Liu B, Liu J

Abstract
Antibiotic abuse and the resulting resistance to antibiotics are serious problems faced by the world. Methods for fast and precise detection of bacterial infections are in urgent need. Here, we report a sensitive and selective probe for diagnosis and treatment of Gram-positive bacterial infection. The probe is made of self-assembling short peptide as the skeleton, a luminogen with aggregation-induced emission (AIEgen) as the responsive fluorescence turn-on motif and vancomycin as the targeting group. In vitro assembly of the probe can turn on its fluorescence and simultaneously enhance reactive oxygen species (ROS) generation. The probe shows great selectivity and sensitivity to Gram-positive bacteria detection in vitro by targeted self-assembly on bacterial surface. In vivo imaging studies of a myositis-bearing BALB/c nude mice model indicate that the probe is suitable for diagnosis and treatment of Gram-positive bacterial infection. The integration of AIEgen and self-assembling peptides represents a potential strategy for disease diagnosis and treatment.

PMID: 32200105 [PubMed - as supplied by publisher]

Related Articles

Rapid and Broad Immune Efficacy of a Recombinant Five-Antigen Vaccine against Staphylococcus Aureus Infection in Animal Models.

Vaccines (Basel). 2020 Mar 18;8(1):

Authors: Zeng H, Yang F, Feng Q, Zhang J, Gu J, Jing H, Cai C, Xu L, Yang X, Xia X, Zeng N, Fan S, Zou Q

Abstract
Staphylococcus aureus (S.aureus) is a leading cause of both healthcare-and community-associated infections globally, which result in severe disease and readily developing antibiotic resistance. Developing an efficacious vaccine against S.aureus is urgently required. In the present study, we selected five conserved antigens, including the secreted factors α-hemolysin (Hla), staphylococcal enterotoxin B (SEB) and the three surface proteins staphylococcal protein A (SpA), iron surface determinant B N2 domain (IsdB-N2) and manganese transport protein C (MntC). They were all well-characterized virulence factor of S. aureus and developed a recombinant five-antigen S. aureus vaccine (rFSAV), rFSAV provided consistent protection in S. aureus lethal sepsis and pneumonia mouse models, and it showed broad immune protection when challenged with a panel of epidemiologically relevant S. aureus strains. Meanwhile, rFSAV immunized mice were able to induce comprehensive cellular and humoral immune responses to reduce bacterial loads, inflammatory cytokine expression, inflammatory cell infiltration and decrease pathology after challenge with a sub-lethal dose of S. aureus. Moreover, the importance of specific antibodies in protection was demonstrated by antibody function tests in vitro and in vivo. Altogether, our data demonstrate that rFSAV is a potentially promising vaccine candidate for defensing against S. aureus infection.

PMID: 32197534 [PubMed - as supplied by publisher]

Nature Communications, Published online: 10 March 2020; doi:10.1038/s41467-020-14336-7

Cell surface proteins mediate the interactions between cells and their extracellular environment. Here the authors design synthetic biomemetic receptor-like sensors that facilitate programmable interactions between bacteria and their target.

Nature Microbiology, Published online: 09 March 2020; doi:10.1038/s41564-020-0687-z

The crystal structure of the RodA–PBP2 complex from Thermus thermophilus elucidates how binding between these two proteins regulates their abilities to polymerize and crosslink peptidoglycan during bacterial cell wall synthesis.

Related Articles

The M-protein of Streptococcus pyogenes strain AP53 retains cell surface functional plasminogen binding after inactivation of the sortase A gene.

J Bacteriol. 2020 Mar 02;:

Authors: Russo B, Ayinuola YA, Singh D, Carothers K, Fischetti VA, FloresMireles A, Lee SW, Ploplis VA, Liang Z, Castellino FJ

Abstract
Streptococcus pyogenes (Lancefield Group A; GAS) is a β-hemolytic human selective pathogen that is responsible for a large number of morbid and mortal infections in humans. For efficient infection, GAS requires different types of surface proteins that provide various mechanisms for evading human innate immune responses, thus enhancing pathogenicity of the bacteria. Many such virulence promoting proteins, including the major surface signature M-protein, are translocated after biosynthesis through the cytoplasmic membrane and temporarily tethered to this membrane via a Type 1 transmembrane domain (TMD) positioned near the COOH-terminus. In these proteins, a sorting signal, LPXTG, is positioned immediately upstream of the TMD, which is cleaved by the membrane-associated transpeptidase, Sortase A (SrtA), leading to the covalent anchoring of these proteins to newly emerging L-Ala-L-Ala crossbridges of the growing peptidoglycan cell wall. Herein, we show that inactivation of the srtA gene in a skin-tropic Pattern D GAS strain (AP53) results in retention of the M-protein in the cell membrane. However, while the isogenic AP53/ΔsrtA strain is attenuated in overall pathogenic properties due to effects on the integrity of the cell membrane, our data show that M-protein nonetheless can extend from the cytoplasmic membrane through the cell wall and then to the surface of the bacteria and thereby retain its important properties of productively binding and activating fluid phase host plasminogen (hPg). The studies presented herein demonstrate an underappreciated additional mechanism of cell surface display of bacterial virulence proteins via their retention in the cell membrane and extension to the GAS surface.IMPORTANCEGroup A Streptococcus pyogenes (GAS) is a human-specific pathogen that produces many surface factors, including its signature M-protein, that contribute to its pathogenicity. M-proteins undergo specific membrane localization and anchoring to the cell wall via the transpeptidase, Sortase A. Herein, we explored the role of Sortase A function on M-protein localization, architecture, and function, employing, a skin-tropic GAS isolate, AP53, which expresses a plasminogen (hPg)-binding M-protein (PAM). We showed that PAM anchored in the cell membrane, due to the targeted inactivation of Sortase A, was nonetheless exposed on the cell surface, and functionally interacted with host hPg. Our demonstration that M-proteins, and possibly other Sortase A-processed proteins that are retained in the cell membrane, can still function to initiate pathogenic processes by this underappreciated mechanism.

PMID: 32123038 [PubMed - as supplied by publisher]

ABSTRACT

Anti-galactose-α-1,3-galactose (anti-α-Gal) antibody is naturally expressed at a high level in humans. It constitutes about 1% of immunoglobulins found in human blood. Here, we designed a live attenuated influenza virus vaccine that can generate α-Gal epitopes in infected cells in order to facilitate opsonization of infected cells, thereby enhancing vaccine-induced immune responses. In the presence of normal human sera, cells infected with this mutant can enhance phagocytosis of human macrophages and cytotoxicity of NK cells in vitro. Using a knockout mouse strain that allows expression of anti-α-Gal antibody in vivo, we showed that this strategy can increase vaccine immunogenicity and the breadth of protection. This vaccine can induce 100% protection against a lethal heterosubtypic group 1 (H5) or group 2 (mouse-adapted H3) influenza virus challenge in the mouse model. In contrast, its heterosubtypic protective effect in wild-type or knockout mice that do not have anti-α-Gal antibody expression is only partial, demonstrating that the enhanced vaccine-induced protection requires anti-α-Gal antibody upon vaccination. Anti-α-Gal-expressing knockout mice immunized with this vaccine produce robust humoral and cell-mediated responses upon a lethal virus challenge. This vaccine can stimulate CD11b^lo/– pulmonary dendritic cells, which are known to be crucial for clearance of influenza virus. Our approach provides a novel strategy for developing next-generation influenza virus vaccines.

IMPORTANCE Influenza A viruses have multiple HA subtypes that are antigenically diverse. Classical influenza virus vaccines are subtype specific, and they cannot induce satisfactory heterosubtypic immunity against multiple influenza virus subtypes. Here, we developed a live attenuated H1N1 influenza virus vaccine that allows the expression of α-Gal epitopes by infected cells. Anti-α-Gal antibody is naturally produced by humans. In the presence of this antibody, human cells infected with this experimental vaccine virus can enhance several antibody-mediated immune responses in vitro. Importantly, mice expressing anti-α-Gal antibody in vivo can be fully protected by this H1N1 vaccine against a lethal H5 or H3 virus challenge. Our work demonstrates a new strategy for using a single influenza virus strain to induce broadly cross-reactive immune responses against different influenza virus subtypes.

Related Articles

The Link between Gut Dysbiosis and Neuroinflammation in Parkinsońs Disease.

Neuroscience. 2020 Feb 26;:

Authors: Baizabal-Carvallo JF, Alonso-Juarez M

Abstract
Parkinsońs disease (PD) is the second most common neurodegenerative disorder. Despite its high frequency the etiology is still unclear; several lines of evidence show that an inflammatory process is implicated in the pathogenesis of this disorder; where activation of brain microglia plays a central role in the damage of dopaminergic neurons of the substantia nigra. Such inflammation has been attributed to the toxic effect of aggregated α-synuclein; however, evidence also implicates an altered gut microbiota (dysbiosis) through the systemic release of endotoxins such as lipopolysaccharide and other metabolic products. This exposure may be enhanced by increased permeability of the intestinal ("leaky gut") and the blood brain barrier; enhancing the entrance of microbiota-produced substances into the central nervous system. In this manuscript, we explore the evidence from clinical and basic science implicating microglia activation by gut dysbiosis and how this phenomenon may impact in the symptomatology and progression of PD.

PMID: 32112917 [PubMed - as supplied by publisher]

Related Articles

Cell-Penetrating Streptavidin: A General Tool for Bifunctional Delivery with Spatiotemporal Control, Mediated by Transport Systems Such as Adaptive Benzopolysulfane Networks.

J Am Chem Soc. 2020 Feb 28;:

Authors: López-Andarias J, Saarbach J, Moreau D, Cheng Y, Derivery E, Laurent Q, González-Gaitán M, Winssinger N, Sakai N, Matile S

Abstract
In this report, cell-penetrating streptavidin (CPS) is introduced to exploit the full power of streptavidin-biotin biotechnology in cellular uptake. For this purpose, transporters, here cyclic oligochalcogenides (COCs), are covalently attached to lysines of wild-type streptavidin. This leaves all four biotin binding sites free for at least bifunctional delivery. To maximize the standards of the quantitative evaluation of cytosolic delivery, the recent chloroalkane penetration assay (CAPA) is coupled with automated high content (HC) imaging, a technique that combines the advantages of fluorescence microscopy and flow cytometry. According to the resulting HC-CAPA, cytosolic delivery of CPS equipped with four benzopolysulfanes was the best among all tested CPSs, also better than the much smaller TAT peptide, the original cell-penetrating peptide from HIV. HaloTag-GFP fusion proteins expressed on mitochondria were successfully targeted using CPS carrying two different biotinylated ligands, HaloTag substrates or anti-GFP nanobodies, interfaced with peptide nucleic acids, flipper force probes, or fluorescent substrates. The delivered substrates could be released from CPS into the cytosol through desthiobiotin-biotin exchange. These results validate CPS as a general tool which enables unrestricted use of streptavidin-biotin biotechnology in cellular uptake.

PMID: 32109058 [PubMed - as supplied by publisher]

Related Articles

Preparation and purification of mono-ubiquitinated proteins using Avi-tagged ubiquitin.

PLoS One. 2020;15(2):e0229000

Authors: Tan W, Murphy VJ, Charron A, van Twest S, Sharp M, Constantinou A, Parker MW, Crismani W, Bythell-Douglas R, Deans AJ

Abstract
Site-specific conjugation of ubiquitin onto a range of DNA repair proteins regulates their critical functions in the DNA damage response. Biochemical and structural characterization of these functions are limited by an absence of tools for the purification of DNA repair proteins in purely the ubiquitinated form. To overcome this barrier, we designed a ubiquitin fusion protein that is N-terminally biotinylated and can be conjugated by E3 RING ligases onto various substrates. Biotin affinity purification of modified proteins, followed by cleavage of the affinity tag leads to release of natively-mono-ubiquitinated substrates. As proof-of-principle, we applied this method to several substrates of mono-ubiquitination in the Fanconi anemia (FA)-BRCA pathway of DNA interstrand crosslink repair. These include the FANCI:FANCD2 complex, the PCNA trimer and BRCA1 modified nucleosomes. This method provides a simple approach to study the role of mono-ubiquitination in DNA repair or any other mono-ubiquitination signaling pathways.

PMID: 32092106 [PubMed - as supplied by publisher]

ABSTRACT

Respiratory viral infections are extremely common, but their impacts on the composition and function of the gut microbiota are poorly understood. We previously observed a significant change in the gut microbiota after viral lung infection. Here, we show that weight loss during respiratory syncytial virus (RSV) or influenza virus infection was due to decreased food consumption, and that the fasting of mice altered gut microbiota composition independently of infection. While the acute phase tumor necrosis factor alpha (TNF-α) response drove early weight loss and inappetence during RSV infection, this was not sufficient to induce changes in the gut microbiota. However, the depletion of CD8⁺ cells increased food intake and prevented weight loss, resulting in a reversal of the gut microbiota changes normally observed during RSV infection. Viral infection also led to changes in the fecal gut metabolome, with a significant shift in lipid metabolism. Sphingolipids, polyunsaturated fatty acids (PUFAs), and the short-chain fatty acid (SCFA) valerate were all increased in abundance in the fecal metabolome following RSV infection. Whether this and the impact of infection-induced anorexia on the gut microbiota are part of a protective anti-inflammatory response during respiratory viral infections remains to be determined.

IMPORTANCE The gut microbiota has an important role in health and disease: gut bacteria can generate metabolites that alter the function of immune cells systemically. Understanding the factors that can lead to changes in the gut microbiome may help to inform therapeutic interventions. This is the first study to systematically dissect the pathway of events from viral lung infection to changes in gut microbiota. We show that the cellular immune response to viral lung infection induces inappetence, which in turn alters the gut microbiome and metabolome. Strikingly, there was an increase in lipids that have been associated with the resolution of disease. This opens up new paths of investigation: first, what is the (presumably secreted) factor made by the T cells that can induce inappetence? Second, is inappetence an adaptation that accelerates recovery from infection, and if so, does the microbiome play a role in this?

ABSTRACT

Cell division is the ultimate process for the propagation of bacteria, and FtsZ is an essential protein used by nearly all bacteria for this function. Chlamydiae belong to a small group of bacteria that lack the universal cell division protein FtsZ but still divide by binary fission. Chlamydial MreB is a member of the shape-determining MreB/Mbl family of proteins responsible for rod shape morphology in Escherichia coli. Chlamydia also encodes a homolog of RodZ, an MreB assembly cytoskeletal protein that links MreB to cell wall synthesis proteins. We hypothesized that MreB directs cell division in Chlamydia and that chlamydial MreB could replace FtsZ function for cell division in E. coli. Overexpression of chlamydial mreB-rodZ in E. coli induced prominent morphological changes with production of large swollen or oval bacteria, eventually resulting in bacterial lysis. Low-level expression of chlamydial mreB-rodZ restored viability of a lethal mreB mutation in E. coli, although the bacteria lost their typical rod shape and grew as rounded cells. When FtsZ activity was inhibited by overexpression of SulA in the mreB mutant of E. coli complemented with chlamydial mreB-rodZ, spherical E. coli grew and divided. Localization studies using a fluorescent fusion chlamydial MreB protein indicated that chlamydial RodZ directs chlamydial MreB to the E. coli division septum. These results demonstrate that chlamydial MreB, in partnership with chlamydial RodZ, acts as a cell division protein. Our findings suggest that an mreB-rodZ-based mechanism allows Chlamydia to divide without the universal division protein FtsZ.

IMPORTANCE The study of Chlamydia growth and cell division is complicated by its obligate intracellular nature and biphasic lifestyle. Chlamydia also lacks the universal division protein FtsZ. We employed the cell division system of Escherichia coli as a surrogate to identify chlamydial cell division proteins. We demonstrate that chlamydial MreB, together with chlamydial RodZ, forms a cell division and growth complex that can replace FtsZ activity and support cell division in E. coli. Chlamydial RodZ plays a major role in directing chlamydial MreB localization to the cell division site. It is likely that the evolution of chlamydial MreB and RodZ to form a functional cell division complex allowed Chlamydia to dispense with its FtsZ-based cell division machinery during genome reduction. Thus, MreB-RodZ represents a possible mechanism for cell division in other bacteria lacking FtsZ.

Scientific Reports, Published online: 11 February 2020; doi:10.1038/s41598-020-59099-9

A Fast and Sensitive Luciferase-based Assay for Antibody Engineering and Design of Chimeric Antigen Receptors

Related Articles

A live auxotrophic vaccine confers mucosal immunity and protection against lethal pneumonia caused by virulent Pseudomonas aeruginosa.

PLoS Pathog. 2020 Feb 10;16(2):e1008311

Authors: Cabral MP, Correia A, Vilanova M, Gärtner F, Moscoso M, García P, Vallejo JA, Pérez A, Francisco-Tomé M, Fuentes-Valverde V, Bou G

Abstract
Pseudomonas aeruginosa is one of the leading causes of nosocomial pneumonia and its associated mortality. Moreover, extensively drug-resistant high-risk clones are globally widespread, presenting a major challenge to the healthcare systems. Despite this, no vaccine is available against this high-concerning pathogen. Here we tested immunogenicity and protective efficacy of an experimental live vaccine against P. aeruginosa pneumonia, consisting of an auxotrophic strain which lacks the key enzyme involved in D-glutamate biosynthesis, a structural component of the bacterial cell wall. As the amounts of free D-glutamate in vivo are trace substances in most cases, blockage of the cell wall synthesis occurs, compromising the growth of this strain, but not its immunogenic properties. Indeed, when delivered intranasally, this vaccine stimulated production of systemic and mucosal antibodies, induced effector memory, central memory and IL-17A-producing CD4+ T cells, and recruited neutrophils and mononuclear phagocytes into the airway mucosa. A significant improvement in mice survival after lung infection caused by ExoU-producing PAO1 and PA14 strains was observed. Nearly one third of the mice infected with the XDR high-risk clone ST235 were also protected. These findings highlight the potential of this vaccine for the control of acute pneumonia caused by this bacterial pathogen.

PMID: 32040500 [PubMed - as supplied by publisher]

Related Articles

Role of the LytSR Two-Component Regulatory System in Staphylococcus lugdunensis Biofilm Formation and Pathogenesis.

Front Microbiol. 2020;11:39

Authors: Dahyot S, Oxaran V, Niepceron M, Dupart E, Legris S, Destruel L, Didi J, Clamens T, Lesouhaitier O, Zerdoumi Y, Flaman JM, Pestel-Caron M

Abstract
Staphylococcus lugdunensis is a coagulase negative Staphylococcus recognized as a virulent pathogen. It is responsible for a wide variety of infections, some of which are associated with biofilm production, such as implanted medical device infections or endocarditis. However, little is known about S. lugdunensis regulation of virulence factor expression. Two-component regulatory systems (TCS) play a critical role in bacterial adaptation, survival, and virulence. Among them, LytSR is widely conserved but has variable roles in different organisms, all connected to metabolism or cell death and lysis occurring during biofilm development. Therefore, we investigated here the functions of LytSR in S. lugdunensis pathogenesis. Deletion of lytSR in S. lugdunensis DSM 4804 strain did not alter either susceptibility to Triton X-100 induced autolysis or death induced by antibiotics targeting cell wall synthesis. Interestingly, ΔlytSR biofilm was characterized by a lower biomass, a lack of tower structures, and a higher rate of dead cells compared to the wild-type strain. Virulence toward Caenorhabditis elegans using a slow-killing assay was significantly reduced for the mutant compared to the wild-type strain. By contrast, the deletion of lytSR had no effect on the cytotoxicity of S. lugdunensis toward the human keratinocyte cell line HaCaT. Transcriptional analyses conducted at mid- and late-exponential phases showed that lytSR deletion affected the expression of 286 genes. Most of them were involved in basic functions such as the metabolism of amino acids, carbohydrates, and nucleotides. Furthermore, LytSR appeared to be involved in the regulation of genes encoding known or putative virulence and colonization factors, including the fibrinogen-binding protein Fbl, the major autolysin AtlL, and the type VII secretion system. Overall, our data suggest that the LytSR TCS is implicated in S. lugdunensis pathogenesis, through its involvement in biofilm formation and potentially by the control of genes encoding putative virulence factors.

PMID: 32038604 [PubMed]

Related Articles

Revealing eukaryotic histone-modifying mechanisms through bacterial infection.

Semin Immunopathol. 2020 Feb 04;:

Authors: Dong W, Hamon MA

Abstract
In the long co-evolution of host-pathogen interaction, bacteria have developed sophisticated strategies to manipulate host cell mechanisms and reprogram host transcription. Targeting chromatin, mainly through post-translational modification (PTM) of histone proteins, is one strategy that has been revealed over the last decade. Indeed, histone modifications play a crucial role in regulating transcription during cell type and stimulus specific responses, making them good targets during infection. Therefore, the study of host-pathogen interactions provides breakthroughs in understanding virulence mechanisms, but also in host cell mechanisms. Although chromatin is regulated by DNA methylation, noncoding RNAs, and post-translational modifications of histones, most studies have concentrated on bacteria-induced histone modifications, which will be the focus of this review. We will discuss the different mechanisms used by bacteria to induce histone PTMs, whether it is through direct targeting of pathogen effector enzymes, or indirectly through modulation of cellular signaling cascade. We will summarize the concepts we learned in cell biology from exploring bacteria-triggered histone modifications, by focusing on the signaling cascades modified by bacteria, bacterial mimics of eukaryotic enzymes, and the novel histone marks imposed upon infection.

PMID: 32020336 [PubMed - as supplied by publisher]

Related Articles

Infection-based chemical screens uncover host-pathogen interactions.

Curr Opin Microbiol. 2020 Feb 06;54:43-50

Authors: Detweiler CS

Abstract
Bacterial pathogens must resist host innate immunity to cause disease. While Gram-negative bacteria have a protective outer membrane, this membrane is subject to host-induced damage that makes these pathogens vulnerable. We developed a high content screening platform that identifies compounds that cause the killing of the bacterial pathogen Salmonella enterica in macrophages. This platform enables the rapid discovery of compounds that work in concert with the macrophage to prevent pathogen survival, as most hit compounds are not active in standard microbiological media and are not pro-drugs. We describe within the platform and the compounds it has found, and consider how they may help us discover new ways to fight infection.

PMID: 32036306 [PubMed - as supplied by publisher]

Related Articles

Bacteria's different ways to recycle their own cell wall.

Int J Med Microbiol. 2019 Nov;309(7):151326

Authors: Mayer C, Kluj RM, Mühleck M, Walter A, Unsleber S, Hottmann I, Borisova M

Abstract
The ability to recover components of their own cell wall is a common feature of bacteria. This was initially recognized in the Gram-negative bacterium Escherichia coli, which recycles about half of the peptidoglycan of its cell wall during one cell doubling. Moreover, E. coli was shown to grow on peptidoglycan components provided as nutrients. A distinguished recycling enzyme of E. coli required for both, recovery of the cell wall sugar N-acetylmuramic acid (MurNAc) of the own cell wall and for growth on external MurNAc, is the MurNAc 6-phosphate (MurNAc 6P) lactyl ether hydrolase MurQ. We revealed however, that most Gram-negative bacteria lack a murQ ortholog and instead harbor a pathway, absent in E. coli, that channels MurNAc directly to peptidoglycan biosynthesis. This "anabolic recycling pathway" bypasses the initial steps of peptidoglycan de novo synthesis, including the target of the antibiotic fosfomycin, thus providing intrinsic resistance to the antibiotic. The Gram-negative oral pathogen Tannerella forsythia is auxotrophic for MurNAc and apparently depends on the anabolic recycling pathway to synthesize its own cell wall by scavenging cell wall debris of other bacteria. In contrast, Gram-positive bacteria lack the anabolic recycling genes, but mostly contain one or two murQ orthologs. Quantification of MurNAc 6P accumulation in murQ mutant cells by mass spectrometry allowed us to demonstrate for the first time that Gram-positive bacteria do recycle their own peptidoglycan. This had been questioned earlier, since peptidoglycan turnover products accumulate in the spent media of Gram-positives. We showed, that these fragments are recovered during nutrient limitation, which prolongs starvation survival of Bacillus subtilis and Staphylococcus aureus. Peptidoglycan recycling in these bacteria however differs, as the cell wall is either cleaved exhaustively and monosaccharide building blocks are taken up (B. subtilis) or disaccharides are released and recycled involving a novel phosphomuramidase (MupG; S.aureus). In B. subtilis also the teichoic acids, covalently bound to the peptidoglycan (wall teichoic acids; WTAs), are recycled. During phosphate limitation, the sn-glycerol-3-phosphate phosphodiesterase GlpQ specifically degrades WTAs of B. subtilis. In S. aureus, in contrast, GlpQ is used to scavenge external teichoic acid sources. Thus, although bacteria generally recover their own cell wall, they apparently apply distinct strategies for breakdown and reutilization of cell wall fragments. This review summarizes our work on this topic funded between 2011 and 2019 by the DFG within the collaborative research center SFB766.

PMID: 31296364 [PubMed - indexed for MEDLINE]

Related Articles

Protective Immunity Elicited by VP1 Chimeric Antigens of Bacterial Ghosts against Hand-Foot-and-Mouth Disease Virus.

Vaccines (Basel). 2020 Feb 01;8(1):

Authors: Gong S, Nan N, Sun Y, He Z, Li J, Chen F, Li T, Ning N, Wang J, Li Z, Luo D, Wang H

Abstract
This study was designed to evaluate the immunogenicity and protective efficacy of two VP1 chimeric antigens of bacterial ghosts. Inoculation of the two VP1 chimeric antigens of bacterial ghosts into BALB/c mice markedly elicited humoral and mucosal immune responses. The specific antibodies induced by the chimeric ghosts protected mice not only against the virus that causes hand-foot-and-mouth disease but also against E. coli O157:H7 bacterial infection. In comparison with the negative control, immunization with the chimeric ghosts protected mice against two LD50 hand-foot-and-mouth disease viral infection. In addition, this specific immunity also protected the pups of pregnant mice immunized with the VP1 chimeric antigens of bacterial ghosts against 20 MLD E. coli O157:H7 infection. Taken together, the results of this study verify for the first time that the VP1 chimeric antigens of bacterial ghosts are target candidates for a new type of vaccine against hand-foot-and-mouth disease. Additionally, this vaccine strategy also elicited a stronger immune response against E. coli O157:H7.

PMID: 32024212 [PubMed]

Related Articles

Structural and conformational behavior of MurE ligase from Salmonella enterica serovar Typhi at different temperature and pH conditions.

Int J Biol Macromol. 2020 Feb 01;:

Authors: Bansal R, Haque A, Hassan I, Ethayathulla AS, Kaur P

Abstract
MurE ligase is known to play a significant role in peptidoglycan biosynthesis. It catalyzes the addition of meso-diaminopimelic acid to nucleotide precursor. The protein can adopt different conformations for its proper functioning. Different environmental conditions can alter the stability and function of enzyme due to their ability to disrupt interactions between different domains. We have explored the pH and temperature dependent conformational changes in MurE ligase from Salmonella Typhi and estimated the protein stability. The study enabled us to decipher the effect of different milieu condition in the enzyme activity. At acidic pH 3.0, StMurE ligase forms molten globule (MG) state and at alkaline pH it is in unfolded state. The different states of StMurE ligase were characterized using various spectroscopic techniques. These techniques including near-UV CD, far-UV CD, ANS fluorescence, Differential Scanning Calorimetry and fluorescence spectroscopy helped to determine the secondary structural changes and detect local conformational changes. The structural analysis using StMurE ligase homology model revealed the change in ionization states of catalytic amino acid residues involved in substrate binding. This study provides an insight into the dynamics states of StMurE ligase at different environmental conditions during bacterial pathogenesis.

PMID: 32018007 [PubMed - as supplied by publisher]

Related Articles

Antibody Binding to the O-Specific Antigen of Pseudomonas aeruginosa O6 Inhibits Cell Growth.

Antimicrob Agents Chemother. 2020 Feb 03;:

Authors: Richard G, MacKenzie CR, Henry KA, Vinogradov E, Hall JC, Hussack G

Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that is inherently resistant to many antibiotics and represents an increasing threat due to the emergence of drug-resistant strains. There is a pressing need to develop innovative antimicrobials against this pathogen. In this study we identified the O-specific antigen (OSA) of P. aeruginosa serotype O6 as a novel target for therapeutic intervention. Binding of monoclonal antibodies and antigen-binding fragments therefrom to O6 OSA leads to rapid outer membrane destabilization and inhibition of cell growth. The antimicrobial effect correlated directly with antibody affinity. Antibody binding to the O-antigen of a second lipopolysaccharide type present in P. aeruginosa or to the LPS core did not affect cell viability. Atomic force microscopy showed that antibody binding to OSA resulted in early flagellum loss, formation of membrane blebs, and eventually complete outer membrane loss. We hypothesize that antibody binding to OSA disrupts a key interaction in the P. aeruginosa outer membrane.

PMID: 32015038 [PubMed - as supplied by publisher]

Related Articles

Defective lytic transglycosylase disrupts cell morphogenesis by hindering cell wall de-O-acetylation in N. meningitidis.

Elife. 2020 Feb 05;9:

Authors: Williams AH, Wheeler R, Deghmane AE, Santecchia I, Schaub RE, Hicham S, Moya Nilges M, Malosse C, Chamot-Rooke J, Haouz A, Dillard JP, Robins WP, Taha MK, Gomperts Boneca I

Abstract
Lytic transglycosylases (LT) are enzymes involved in peptidoglycan (PG) remodeling. However, their contribution to cell wall-modifying complexes and their potential as antimicrobial drug targets remain unclear. Here, we determined a high-resolution structure of the LT, an outer membrane lipoprotein from Neisseria species with a disordered active site helix (alpha helix 30). We show that deletion of the conserved alpha-helix 30 interferes with the integrity of the cell wall, disrupts cell division, cell separation, and impairs the fitness of the human pathogen Neisseria meningitidis during infection. Additionally, deletion of alpha-helix 30 results in hyperacetylated PG, suggesting this LtgA variant affects the function of the PG de-O-acetylase (Ape 1). Our study revealed that Ape 1 requires LtgA for optimal function, demonstrating that LTs can modulate the activity of their protein-binding partner. We show that targeting specific domains in LTs can be lethal, which opens the possibility that LTs are useful drug-targets.

PMID: 32022687 [PubMed - as supplied by publisher]

Related Articles

Identification of a Potential Inhibitor Targeting MurC Ligase of the Drug Resistant Pseudomonas aeruginosa Strain through Structure-Based Virtual Screening Approach and In Vitro Assay.

Curr Pharm Biotechnol. 2019;20(14):1203-1212

Authors: Messaoudi A, Zoghlami M, Basharat Z, Sadfi-Zouaoui N

Abstract
BACKGROUND & OBJECTIVE: Pseudomonas aeruginosa shows resistance to a large number of antibiotics, including carbapenems and third generation cephalosporin. According to the World Health Organization global report published in February 2017, Pseudomonas aeruginosa is on the priority list among resistant bacteria, for which new antibiotics are urgently needed. Peptidoglycan serves as a good target for the discovery of novel antimicrobial drugs.
METHODS: Biosynthesis of peptidoglycan is a multi-step process involving four mur enzymes. Among these enzymes, UDP-N-acetylmuramate-L-alanine ligase (MurC) is considered to be an excellent target for the design of new classes of antimicrobial inhibitors in gram-negative bacteria.
RESULTS: In this study, a homology model of Pseudomonas aeruginosa MurC ligase was generated and used for virtual screening of chemical compounds from the ZINC Database. The best screened inhibitor i.e. N, N-dimethyl-2-oxo-2,3-dihydro-1H-1,3-benzodiazole-5-sulfonamide was then validated experimentally through inhibition assay.
CONCLUSION: The presented results based on combined computational and in vitro analysis open up new horizons for the development of novel antimicrobials against this pathogen.

PMID: 31333120 [PubMed - indexed for MEDLINE]

Related Articles

Listeria monocytogenes exploits host exocytosis to promote cell-to-cell spread.

Proc Natl Acad Sci U S A. 2020 Feb 03;:

Authors: Dowd GC, Mortuza R, Bhalla M, Van Ngo H, Li Y, Rigano LA, Ireton K

Abstract
The facultative intracellular pathogen Listeria monocytogenes uses an actin-based motility process to spread within human tissues. Filamentous actin from the human cell forms a tail behind bacteria, propelling microbes through the cytoplasm. Motile bacteria remodel the host plasma membrane into protrusions that are internalized by neighboring cells. A critical unresolved question is whether generation of protrusions by Listeria involves stimulation of host processes apart from actin polymerization. Here we demonstrate that efficient protrusion formation in polarized epithelial cells involves bacterial subversion of host exocytosis. Confocal microscopy imaging indicated that exocytosis is up-regulated in protrusions of Listeria in a manner that depends on the host exocyst complex. Depletion of components of the exocyst complex by RNA interference inhibited the formation of Listeria protrusions and subsequent cell-to-cell spread of bacteria. Additional genetic studies indicated important roles for the exocyst regulators Rab8 and Rab11 in bacterial protrusion formation and spread. The secreted Listeria virulence factor InlC associated with the exocyst component Exo70 and mediated the recruitment of Exo70 to bacterial protrusions. Depletion of exocyst proteins reduced the length of Listeria protrusions, suggesting that the exocyst complex promotes protrusion elongation. Collectively, these results demonstrate that Listeria exploits host exocytosis to stimulate intercellular spread of bacteria.

PMID: 32015134 [PubMed - as supplied by publisher]