Results
- Showing results for:
- Reset all filters
Search results
-
Journal articlePortaliou AG, Tsolis KC, Loos MS, et al., 2017,
Hierarchical protein targeting and secretion is controlled by an affinity switch in the type III secretion system of enteropathogenic <i>Escherichia coli</i>
, EMBO JOURNAL, Vol: 36, Pages: 3517-3531, ISSN: 0261-4189- Author Web Link
- Cite
- Citations: 43
-
Journal articleCepeda-Molero M, Berger CN, Walsham ADS, et al., 2017,
Attaching and effacing (A/E) lesion formation by enteropathogenic E. coli on human intestinal mucosa is dependent on non-LEE effectors
, PLoS Pathogens, Vol: 13, ISSN: 1553-7366Enteropathogenic E. coli (EPEC) is a human pathogen that causes acute and chronic pediatric diarrhea. The hallmark of EPEC infection is the formation of attaching and effacing (A/E) lesions in the intestinal epithelium. Formation of A/E lesions is mediated by genes located on the pathogenicity island locus of enterocyte effacement (LEE), which encode the adhesin intimin, a type III secretion system (T3SS) and six effectors, including the essential translocated intimin receptor (Tir). Seventeen additional effectors are encoded by genes located outside the LEE, in insertion elements and prophages. Here, using a stepwise approach, we generated an EPEC mutant lacking the entire effector genes (EPEC0) and intermediate mutants. We show that EPEC0 contains a functional T3SS. An EPEC mutant expressing intimin but lacking all the LEE effectors but Tir (EPEC1) was able to trigger robust actin polymerization in HeLa cells and mucin-producing intestinal LS174T cells. However, EPEC1 was unable to form A/E lesions on human intestinal in vitro organ cultures (IVOC). Screening the intermediate mutants for genes involved in A/E lesion formation on IVOC revealed that strains lacking non-LEE effector/s have a marginal ability to form A/E lesions. Furthermore, we found that Efa1/LifA proteins are important for A/E lesion formation efficiency in EPEC strains lacking multiple effectors. Taken together, these results demonstrate the intricate relationships between T3SS effectors and the essential role non-LEE effectors play in A/E lesion formation on mucosal surfaces.
-
Journal articleWen KY, Cameron L, Chappell J, et al., 2017,
A Cell-Free Biosensor for Detecting Quorum Sensing Molecules in P. aeruginosa-Infected Respiratory Samples.
, ACS Synthetic Biology, Vol: 6, Pages: 2293-2301, ISSN: 2161-5063Synthetic biology designed cell-free biosensors are a promising new tool for the detection of clinically relevant biomarkers in infectious diseases. Here, we report that a modular DNA-encoded biosensor in cell-free protein expression systems can be used to measure a bacterial biomarker of Pseudomonas aeruginosa infection from human sputum samples. By optimizing the cell-free system and sample extraction, we demonstrate that the quorum sensing molecule 3-oxo-C12-HSL in sputum samples from cystic fibrosis lungs can be quantitatively measured at nanomolar levels using our cell-free biosensor system, and is comparable to LC-MS measurements of the same samples. This study further illustrates the potential of modular cell-free biosensors as rapid, low-cost detection assays that can inform clinical practice.
-
Journal articleBerger C, Crepin V, Roumeliotis TI, et al., 2017,
Citrobacter rodentium subverts ATP flux 1 and cholesterol homeostasis in 2 intestinal epithelial cell in vivo
, Cell Metabolism, Vol: 26, Pages: 738-752.e6, ISSN: 1550-4131The intestinal epithelial cells (IECs) that line the gut form a robust line of defense against ingested pathogens. We investigated the impact of infection with the enteric pathogen Citrobacter rodentium on mouse IEC metabolism using global proteomic and targeted metabolomics and lipidomics. The major signatures of the infection were upregulation of the sugar transporter Sglt4, aerobic glycolysis, and production of phosphocreatine, which mobilizes cytosolic energy. In contrast, biogenesis of mitochondrial cardiolipins, essential for ATP production, was inhibited, which coincided with increased levels of mucosal O2 and a reduction in colon-associated anaerobic commensals. In addition, IECs responded to infection by activating Srebp2 and the cholesterol biosynthetic pathway. Unexpectedly, infected IECs also upregulated the cholesterol efflux proteins AbcA1, AbcG8, and ApoA1, resulting in higher levels of fecal cholesterol and a bloom of Proteobacteria. These results suggest that C. rodentium manipulates host metabolism to evade innate immune responses and establish a favorable gut ecosystem.
-
Journal articleMcCarthy RR, Valentini M, Filloux A, 2017,
Contribution of Cyclic di-GMP in the Control of Type III and Type VI Secretion in Pseudomonas aeruginosa.
, Methods Mol Biol, Vol: 1657, Pages: 213-224Bacteria produce toxins to enhance their competitiveness in the colonization of an environment as well as during an infection. The delivery of toxins into target cells is mediated by several types of secretion systems, among them our focus is Type III and Type VI Secretion Systems (T3SS and T6SS, respectively). A thorough methodology is provided detailing how to identify if cyclic di-GMP signaling plays a role in the P. aeruginosa toxin delivery mediated by T3SS or T6SS. This includes in vitro preparation of the samples for Western blot analysis aiming at detecting possible c-di-GMP-dependent T3SS/T6SS switch, as well as in vivo analysis using the model organism Galleria mellonella to demonstrate the ecological and pathogenic consequence of the switch between these two secretion systems.
-
Journal articleKarampatzakis A, Song CZ, Allsopp LP, et al., 2017,
Probing the internal micromechanical properties of Pseudomonas aeruginosa biofilms by Brillouin imaging.
, NPJ Biofilms Microbiomes, Vol: 3, ISSN: 2055-5008Biofilms are organised aggregates of bacteria that adhere to each other or surfaces. The matrix of extracellular polymeric substances that holds the cells together provides the mechanical stability of the biofilm. In this study, we have applied Brillouin microscopy, a technique that is capable of measuring mechanical properties of specimens on a micrometre scale based on the shift in frequency of light incident upon a sample due to thermal fluctuations, to investigate the micromechanical properties of an active, live Pseudomonas aeruginosa biofilm. Using this non-contact and label-free technique, we have extracted information about the internal stiffness of biofilms under continuous flow. No correlation with colony size was found when comparing the averages of Brillouin shifts of two-dimensional cross-sections of randomly selected colonies. However, when focusing on single colonies, we observed two distinct spatial patterns: in smaller colonies, stiffness increased towards their interior, indicating a more compact structure of the centre of the colony, whereas, larger (over 45 μm) colonies were found to have less stiff interiors.
-
Journal articleHeeb S, Camara M, Filloux A, et al., 2017,
Professor Dieter Haas (1945-2017)
, FEMS Microbiology Reviews, Vol: 41, Pages: 597-598, ISSN: 0168-6445 -
Journal articleJakobsen TH, Warming AN, Vejborg RM, et al., 2017,
A broad range quorum sensing inhibitor working through sRNA inhibition
, Scientific Reports, Vol: 7, ISSN: 2045-2322For the last decade, chemical control of bacterial virulence has received considerable attention. Ajoene, a sulfur-rich molecule from garlic has been shown to reduce expression of key quorum sensing regulated virulence factors in the opportunistic pathogen Pseudomonas aeruginosa. Here we show that the repressing effect of ajoene on quorum sensing occurs by inhibition of small regulatory RNAs (sRNA) in P. aeruginosa as well as in Staphylococcus aureus, another important human pathogen that employs quorum sensing to control virulence gene expression. Using various reporter constructs, we found that ajoene lowered expression of the sRNAs RsmY and RsmZ in P. aeruginosa and the small dual-function regulatory RNA, RNAIII in S. aureus, that controls expression of key virulence factors. We confirmed the modulation of RNAIII by RNA sequencing and found that the expression of many QS regulated genes encoding virulence factors such as hemolysins and proteases were lowered in the presence of ajoene in S. aureus. Importantly, our findings show that sRNAs across bacterial species potentially may qualify as targets of anti-virulence therapy and that ajoene could be a lead structure in search of broad-spectrum compounds transcending the Gram negative-positive borderline.
-
Journal articleSarkar P, Switzer A, Peters C, et al., 2017,
Phenotypic consequences of RNA polymerase dysregulation in Escherichiacoli
, Nucleic Acids Research, Vol: 45, Pages: 11131-11143, ISSN: 1362-4962Many bacterial adaptive responses to changes in growth conditions due to biotic and abiotic factors involve reprogramming of gene expression at the transcription level. The bacterial RNA polymerase (RNAP), which catalyzes transcription, can thus be considered as the major mediator of cellular adaptive strategies. But how do bacteria respond if a stress factor directly compromises the activity of the RNAP? We used a phage-derived small protein to specifically perturb bacterial RNAP activity in exponentially growing Escherichia coli. Using cytological profiling, tracking RNAP behavior at single-molecule level and transcriptome analysis, we reveal that adaptation to conditions that directly perturb bacterial RNAP performance can result in a biphasic growth behavior and thereby confer the ‘adapted’ bacterial cells an enhanced ability to tolerate diverse antibacterial stresses. The results imply that while synthetic transcriptional rewiring may confer bacteria with the intended desirable properties, such approaches may also collaterally allow them to acquire undesirable traits.
-
Journal articlerouse S, hawthorne, berry, et al., 2017,
A new class of hybrid secretion system is employed in Pseudomonas amyloid biogenesis
, Nature Communications, Vol: 8, ISSN: 2041-1723Gram-negative bacteria possess specialised biogenesis machineries that facilitate the export of amyloid subunits for construction of a biofilm matrix. The secretion of bacterial functional amyloid requires a bespoke outer-membrane protein channel through which unfolded amyloid substrates are translocated. Here, we combine X-ray crystallography, native mass spectrometry, single-channel electrical recording, molecular simulations and circular dichroism measurements to provide high-resolution structural insight into the functional amyloid transporter from Pseudomonas, FapF. FapF forms a trimer of gated β-barrel channels in which opening is regulated by a helical plug connected to an extended coil-coiled platform spanning the bacterial periplasm. Although FapF represents a unique type of secretion system, it shares mechanistic features with a diverse range of peptide translocation systems. Our findings highlight alternative strategies for handling and export of amyloid protein sequences.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.
Where we are
CBRB
Imperial College London
Flowers Building
Exhibition Road
London SW7 2AZ