791 research outputs found
(p)ppGpp and CodY promote Enterococcus faecalis virulence in a murine model of catheter-associated urinary tract infection
ABSTRACT In Firmicutes, the nutrient-sensing regulators (p)ppGpp, the effector molecule of the stringent response, and CodY work in tandem to maintain bacterial fitness during infection. Here, we tested (p)ppGpp and codY mutant strains of Enterococcus faecalis in a catheter-associated urinary tract infection (CAUTI) mouse model and used global transcriptional analysis to investigate the relationship of (p)ppGpp and CodY. The absence of (p)ppGpp or single inactivation of codY led to lower bacterial loads in catheterized bladders and diminished biofilm formation on fibrinogen-coated surfaces under in vitro and in vivo conditions. Single inactivation of the bifunctional (p)ppGpp synthetase/hydrolase rel did not affect virulence, supporting previous evidence that the association of (p)ppGpp with enterococcal virulence is not dependent on the activation of the stringent response. Inactivation of codY in the (p)ppGpp0 strain restored E. faecalis virulence in the CAUTI model as well as the ability to form biofilms in vitro. Transcriptome analysis revealed that inactivation of codY restores, for the most part, the dysregulated metabolism of (p)ppGpp0 cells. While a clear linkage between (p)ppGpp and CodY with expression of virulence factors could not be established, targeted transcriptional analysis indicates that a possible association between (p)ppGpp and c-di-AMP signaling pathways in response to the conditions found in the bladder may play a role in enterococcal CAUTI. Collectively, data from this study identify the (p)ppGpp-CodY network as an important contributor to enterococcal virulence in catheterized mouse bladder and support that basal (p)ppGpp pools and CodY promote virulence through maintenance of a balanced metabolism under adverse conditions. IMPORTANCE Catheter-associated urinary tract infections (CAUTIs) are one of the most frequent types of infection found in the hospital setting that can develop into serious and potentially fatal bloodstream infections. One of the infectious agents that frequently causes complicated CAUTI is the bacterium Enterococcus faecalis, a leading cause of hospital-acquired infections that are often difficult to treat due to the exceptional multidrug resistance of some isolates. Understanding the mechanisms by which E. faecalis causes CAUTI will aid in the discovery of new druggable targets to treat these infections. In this study, we report the importance of two nutrient-sensing bacterial regulators, named (p)ppGpp and CodY, for the ability of E. faecalis to infect the catheterized bladder of mice
Evolutionary fine-tuning of conformational ensembles in FimH during host-pathogen interactions
Positive selection in the two-domain type 1 pilus adhesin FimH enhances Escherichia coli fitness in urinary tract infection (UTI). We report a comprehensive atomic-level view of FimH in two-state conformational ensembles in solution, composed of one low-affinity tense (T) and multiple high-affinity relaxed (R) conformations. Positively selected residues allosterically modulate the equilibrium between these two conformational states, each of which engages mannose through distinct binding orientations. A FimH variant that only adopts the R state is severely attenuated early in a mouse model of uncomplicated UTI but is proficient at colonizing catheterized bladders in vivo or bladder transitional-like epithelial cells in vitro. Thus, the bladder habitat has barrier(s) to R state–mediated colonization possibly conferred by the terminally differentiated bladder epithelium and/or decoy receptors in urine. Together, our studies reveal the conformational landscape in solution, binding mechanisms, and adhesive strength of an allosteric two-domain adhesin that evolved “moderate” affinity to optimize persistence in the bladder during UTI
Peculiarities of anharmonic lattice dynamics and thermodynamics of alkaline-earth metals
The calculations are performed for a broad range of the properties of Ca and
Sr in the fcc and bcc phases. A detailed information on the magnitude and
character of temperature dependence of anharmonic effects in the lattice
dynamics over the entire Brillouin zone (frequency shifts and phonon damping,
Gruneisen parameters) is given. A detailed comparison of the computational
results for the heat capacity and thermal expansion with the experimental data
is carried out; the theoretical results are in good agreement with the
experiment.Comment: 16 pages, 19 Postscript figures, Revte
The catabolite repressor protein-cyclic AMP complex regulates csgD and biofilm formation in uropathogenic Escherichia coli
The extracellular matrix protects Escherichia coli from immune cells, oxidative stress, predation, and other environmental stresses. Production of the E. coli extracellular matrix is regulated by transcription factors that are tuned to environmental conditions. The biofilm master regulator protein CsgD upregulates curli and cellulose, the two major polymers in the extracellular matrix of uropathogenic E. coli (UPEC) biofilms. We found that cyclic AMP (cAMP) regulates curli, cellulose, and UPEC biofilms through csgD. The alarmone cAMP is produced by adenylate cyclase (CyaA), and deletion of cyaA resulted in reduced extracellular matrix production and biofilm formation. The catabolite repressor protein (CRP) positively regulated csgD transcription, leading to curli and cellulose production in the UPEC isolate, UTI89. Glucose, a known inhibitor of CyaA activity, blocked extracellular matrix formation when added to the growth medium. The mutant strains ΔcyaA and Δcrp did not produce rugose biofilms, pellicles, curli, cellulose, or CsgD. Three putative CRP binding sites were identified within the csgD-csgB intergenic region, and purified CRP could gel shift the csgD-csgB intergenic region. Additionally, we found that CRP binded upstream of kpsMT, which encodes machinery for K1 capsule production. Together our work shows that cAMP and CRP influence E. coli biofilms through transcriptional regulation of csgD. IMPORTANCE The catabolite repressor protein (CRP)-cyclic AMP (cAMP) complex influences the transcription of ∼7% of genes on the Escherichia coli chromosome (D. Zheng, C. Constantinidou, J. L. Hobman, and S. D. Minchin, Nucleic Acids Res 32:5874–5893, 2004, https://dx.doi.org/10.1093/nar/gkh908). Glucose inhibits E. coli biofilm formation, and ΔcyaA and Δcrp mutants show impaired biofilm formation (D. W. Jackson, J.W. Simecka, and T. Romeo, J Bacteriol 184:3406–3410, 2002, https://dx.doi.org/10.1128/JB.184.12.3406-3410.2002). We determined that the cAMP-CRP complex regulates curli and cellulose production and the formation of rugose and pellicle biofilms through csgD. Additionally, we propose that cAMP may work as a signaling compound for uropathogenic E. coli (UPEC) to transition from the bladder lumen to inside epithelial cells for intracellular bacterial community formation through K1 capsule regulation
1/3-Octave Analysis of Core/Combustor-Noise Measurements for the DGEN Aeropropulsion Research Turbofan with Application to Noise Prediction
This work continues the analysis of data obtained during a 2017 NASA DGEN Aeropropulsion Research Turbofan (DART) core/combustor-noise baseline test in the NASA GRC Aero-Acoustic Propulsion Laboratory (AAPL). The DART is a cost-efficient testbed for the study of core-noise physics and mitigation. Acoustic data were simultaneously acquired using the AAPL overhead microphone array in the engine aft-quadrant farfield, a single midfield microphone, and two infinite-tube-probe sensors for unsteady pressures at the core-nozzle exit. The data are here examined on an 1/3-octave basis as a first step in extending and improving core-noise prediction capability
Atomic-scale surface demixing in a eutectic liquid BiSn alloy
Resonant x-ray reflectivity of the surface of the liquid phase of the
BiSn eutectic alloy reveals atomic-scale demixing extending over
three near-surface atomic layers. Due to the absence of underlying atomic
lattice which typically defines adsorption in crystalline alloys, studies of
adsorption in liquid alloys provide unique insight on interatomic interactions
at the surface. The observed composition modulation could be accounted for
quantitatively by the Defay-Prigogine and Strohl-King multilayer extensions of
the single-layer Gibbs model, revealing a near-surface domination of the
attractive Bi-Sn interaction over the entropy.Comment: 4 pages (two-column), 3 figures, 1 table; Added a figure, updated
references, discussion; accepted at Phys. Rev. Let
Thermodynamic properties of binary HCP solution phases from special quasirandom structures
Three different special quasirandom structures (SQS) of the substitutional
hcp binary random solutions (, 0.5, and 0.75) are
presented. These structures are able to mimic the most important pair and
multi-site correlation functions corresponding to perfectly random hcp
solutions at those compositions. Due to the relatively small size of the
generated structures, they can be used to calculate the properties of random
hcp alloys via first-principles methods. The structures are relaxed in order to
find their lowest energy configurations at each composition. In some cases, it
was found that full relaxation resulted in complete loss of their parental
symmetry as hcp so geometry optimizations in which no local relaxations are
allowed were also performed. In general, the first-principles results for the
seven binary systems (Cd-Mg, Mg-Zr, Al-Mg, Mo-Ru, Hf-Ti, Hf-Zr, and Ti-Zr) show
good agreement with both formation enthalpy and lattice parameters measurements
from experiments. It is concluded that the SQS's presented in this work can be
widely used to study the behavior of random hcp solutions.Comment: 15 pages, 8 figure
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