Two-component systems required for virulence in Pseudomonas aeruginosa

This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.Pseudomonas aeruginosa is a versatile opportunistic pathogen capable of infecting a broad range of hosts, in addition to thriving in a broad range of environmental conditions outside of hosts. With this versatility comes the need to tightly regulate its genome to optimise its gene expression and behaviour to the prevailing conditions. Two-component systems (TCSs) comprising sensor kinases and response regulators, play a major role in this regulation. This minireview discusses the growing number of two-component systems that have been implicated in the virulence of Pseudomonas aeruginosa, with a special focus on the emerging theme of multikinase networks, which are networks comprising multiple sensor kinases working together, sensing and integrating multiple signals to decide upon the best response. The networks covered in depth regulate processes such as the switch between acute and chronic virulence (GacS network), the Cup fimbriae (Roc network and Rcs/Pvr network), the aminoarabinose modification of lipopolysaccharide (a network involving the PhoQP and PmrBA TCSs), twitching motility and virulence (a network formed from the Chp chemosensory pathway and the FimS/AlgR TCS), and biofilm formation (Wsp chemosensory pathway). In addition, we highlight the important interfaces between these systems and secondary messenger signals such as cAMP and c-di-GMP.This work was supported by the Medical Research Council (MRC) [grant number MR/M020045/1], the Leverhulme Trust [grant number RPG-2014-228] and the RoseTrees Trust [grant number M328]

Evolutionary diversification of the RomR protein of the invasive deltaproteobacterium, Bdellovibrio bacteriovorus

This is the final version. Available on open access from Nature Research via the DOI in this recordBdellovibrio bacteriovorus is a predatory deltaproteobacterium that encounters individual Gram-negative prey bacteria with gliding or swimming motility, and then is able to invade such prey cells via type IVa pilus-dependent mechanisms. Movement control (pili or gliding) in other deltaproteobacteria, such as the pack hunting Myxococcus xanthus, uses a response regulator protein, RomRMx (which dynamically relocalises between the cell poles) and a GTPase, MglAMx, previously postulated as an interface between the FrzMx chemosensory system and gliding or pilus-motility apparatus, to produce regulated bidirectional motility. In contrast, B. bacteriovorus predation is a more singular encounter between a lone predator and prey; contact is always via the piliated, non-flagellar pole of the predator, involving MglABd, but no Frz system. In this new study, tracking fluorescent RomRBd microscopically during predatory growth shows that it does not dynamically relocalise, in contrast to the M. xanthus protein; instead having possible roles in growth events. Furthermore, transcriptional start analysis, site-directed mutagenesis and bacterial two-hybrid interaction studies, indicate an evolutionary loss of RomRBd activation (via receiver domain phosphorylation) in this lone hunting bacterium, demonstrating divergence from its bipolar role in motility in pack-hunting M. xanthus and further evolution that may differentiate lone from pack predators.Leverhulme TrustMedical Research Council (MRC)Biotechnology and Biological Sciences Research Council (BBSRC

Multiple communication mechanisms between sensor kinases are crucial for virulence in Pseudomonas aeruginosa

Bacteria and many non-metazoan Eukaryotes respond to stresses and threats using two-component systems (TCSs) comprising sensor kinases (SKs) and response regulators (RRs). Multikinase networks, where multiple SKs work together, detect and integrate different signals to control important lifestyle decisions such as sporulation and virulence. Here, we study interactions between two SKs from Pseudomonas aeruginosa, GacS and RetS, which control the switch between acute and chronic virulence. We demonstrate three mechanisms by which RetS attenuates GacS signalling: RetS takes phosphoryl groups from GacS-P; RetS has transmitter phosphatase activity against the receiver domain of GacS-P; and RetS inhibits GacS autophosphorylation. These mechanisms play important roles in vivo and during infection, and exemplify an unprecedented degree of signal processing by SKs that may be exploited in other multikinase networks

Insights into the atypical autokinase activity of the Pseudomonas aeruginosa GacS histidine kinase and its interaction with RetS

This is the author accepted manuscriptVirulence in Pseudomonas aeruginosa (PA) depends on complex regulatory networks, involving phophosphorelay systems based on two-component systems (TCSs). The GacS/GacA TCS is a master regulator of biofilm formation, swarming motility and virulence. GacS is a membraneassociated unorthodox histidine kinase (HK) whose phosphorelay signaling pathway is inhibited by the RetS hybrid HK. Here we provide structural and functional insights into the interaction of GacS with RetS. The structure of the GacS HAMP-H1 cytoplasmic regions reveals an unusually elongated homodimer marked by a 135 Å long helical bundle formed by the HAMP, the signaling helix (S-helix) and the DHp subdomain. The HAMP and S-helix regions are essential for GacS signaling and contribute to the GacS/RetS binding interface. The structure of the GacS D1 domain together with the discovery of an unidentified functional ND domain, essential for GacS full autokinase activity, unveils signature motifs in GacS required for its atypical autokinase mechanism.ANR project REGALADANR project MIdiaZONEVaincre la mucovisicdose - Gregory LemarchalFrench Infrastructures for Integrated Structural BiologyFrench Infrastructures for ProteomicsGIS IBiSARégion AlsaceCNRSAix-Marseille UniversityUniversity of Strasbour

Understanding COVID-19 Dynamics and the Effects of Interventions in the Philippines: A Mathematical Modelling Study

Background COVID-19 initially caused less severe outbreaks in many low- and middle-income countries (LMIC) compared with many high-income countries; possibly because of differing demographics; socioeconomics; surveillance; and policy responses. Here; we investigate the role of multiple factors on COVID-19 dynamics in the Philippines; a LMIC that has had a relatively severe COVID-19 outbreak. Methods We applied an age-structured compartmental model that incorporated time-varying mobility; testing; and personal protective behaviors (through a “Minimum Health Standards” policy; MHS) to represent the first wave of the Philippines COVID-19 epidemic nationally and for three highly affected regions (Calabarzon; Central Visayas; and the National Capital Region). We estimated effects of control measures; key epidemiological parameters; and interventions. Findings Population age structure; contact rates; mobility; testing; and MHS were sufficient to explain the Philippines epidemic based on the good fit between modelled and reported cases; hospitalisations; and deaths. The model indicated that MHS reduced the probability of transmission per contact by 13-27%. The February 2021 case detection rate was estimated at ~8%; population recovered at ~9%; and scenario projections indicated high sensitivity to MHS adherence. Interpretation COVID-19 dynamics in the Philippines are driven by age; contact structure; mobility; and MHS adherence. Continued compliance with low-cost MHS should help the Philippines control the epidemic until vaccines are widely distributed; but disease resurgence may be occurring due to a combination of low population immunity and detection rates and new variants of concern

Cryptococcus neoformans rapidly invades the murine brain by sequential breaching of airway and endothelial tissues barriers, followed by engulfment by microglia

This is the final version. Available on open access from the American Society for Microbiology via the DOI in this recordCryptococcus neoformans causes lethal meningitis and accounts for approximately 10%-15% of AIDS-associated deaths worldwide. There are major gaps in our understanding of how this fungus invades the mammalian brain. To investigate the dynamics of C. neoformans tissue invasion, we mapped fungal localization and host cell interactions in infected brain, lung, and upper airways using mouse models of systemic and airway infection. To enable this, we developed an in situ imaging pipeline capable of measuring large volumes of tissue while preserving anatomical and cellular information by combining thick tissue sections, tissue clarification, and confocal imaging. We confirm high fungal burden in mouse upper airway after nasal inoculation. Yeast in turbinates were frequently titan cells, with faster kinetics than reported in mouse lungs. Importantly, we observed one instance of fungal cells enmeshed in lamina propria of the upper airways, suggesting penetration of airway mucosa as a possible route of tissue invasion and dissemination to the bloodstream. We extend previous literature positing bloodstream dissemination of C. neoformans, by finding viable fungi in the bloodstream of mice a few days after intranasal infection. As early as 24 h post systemic infection, the majority of C. neoformans cells traversed the blood-brain barrier, and were engulfed or in close proximity to microglia. Our work presents a new method for investigating microbial invasion, establishes that C. neoformans can breach multiple tissue barriers within the first days of infection, and demonstrates microglia as the first cells responding to C. neoformans invasion of the brain.IMPORTANCECryptococcal meningitis causes 10%-15% of AIDS-associated deaths globally. Still, brain-specific immunity to cryptococci is a conundrum. By employing innovative imaging, this study reveals what occurs during the first days of infection in brain and in airways. We found that titan cells predominate in upper airways and that cryptococci breach the upper airway mucosa, which implies that, at least in mice, the upper airways are a site for fungal dissemination. This would signify that mucosal immunity of the upper airway needs to be better understood. Importantly, we also show that microglia, the brain-resident macrophages, are the first responders to infection, and microglia clusters are formed surrounding cryptococci. This study opens the field to detailed molecular investigations on airway immune response, how fungus traverses the blood-brain barrier, how microglia respond to infection, and ultimately how microglia monitor the blood-brain barrier to preserve brain function

Effect of growth temperature on the structural, optical and luminescence properties of cadmium telluride nanoparticles

Cadmium telluride (CdTe) has been successfully prepared by a simple wet chemical process at different reaction temperatures. Temperature is one parameter that thermodynamically plays an important role in controlling the growth rate, morphology, size and size distribution of the as-prepared nanoparticles (NPs). Effect of this parameter was investigated on the growth, structural and optical properties of CdTe NPs. It was observed that the Powder X-ray diffraction (XRD) pattern for samples prepared at 50 °C had many impurities from unreacted precursors while those prepared at > 100 °C displayed polycrystalline NPs. The XRD results revealed that the structure of the CdTe NPs was cubic with the planes (111), (220), (311) being the main observed peaks. The crystallite sizes obtained from Scherrer formula increased with the increase in growth temperature (2.86–3.62 nm grown at 50–200 °C respectively). The scanning electron microscopy micrographs showed that the morphology of the nanoparticles possessed spherical-shaped particles over the entire surface. This was further confirmed by high resolution transmission electron microscopy micrographs which also displayed increase in the particle size with an increase in the growth temperature. In the optic study, the photoluminescence (PL) spectra displayed a red shift (540–560 nm) in emission as growth temperature increased from 50 to 200 °C. The highest PL peak intensity was realized at a growth temperature of 150 °C. Absorption band maxima were observed to shift towards longer wavelength for higher growth temperatures. The optical band gap decreased with increase in the growth temperature from 2.67 to 2.08 eV for 50–200 °C respectively

Introduction: Shakespeare's public spheres

Habermas’ sense of a “cultural Public Sphere” is a notoriously complex term and, when applied to Early Modern cultures, needs careful definition. This essay both introduces the variety of methods by which we might approach playtexts with a view to their public – auditory – impact and contributes to a debate about an audience's understanding of Shakespeare's plays. By selecting two words and their spread of use in one play, Twelfth Night, we might appreciate the potential for meaningful ambiguity latent in how we hear the language of live performance. If we search for how certain terms (in this case, the cluster of semes derived from repetitions of “fancy” and “play”), we might find at times incompatible senses, yet we get near to appreciating the range of Early Modern dramatic language

Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration