The human pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 colonizes human and animal gut via formation of attaching and effacing lesions. EHEC strains use a type III secretion system to ...translocate a battery of effector proteins into the mammalian host cell, which subvert diverse signal transduction pathways implicated in actin dynamics, phagocytosis, and innate immunity. The genomes of sequenced EHEC O157:H7 strains contain two copies of the effector protein gene nleH, which share 49% sequence similarity with the gene for the Shigella effector OspG, recently implicated in inhibition of migration of the transcriptional regulator NF-κB to the nucleus. In this study we investigated the role of NleH during EHEC O157:H7 infection of calves and lambs. We found that while EHEC ΔnleH colonized the bovine gut more efficiently than the wild-type strain, in lambs the wild-type strain exhibited a competitive advantage over the mutant during mixed infection. Using the mouse pathogen Citrobacter rodentium, which shares many virulence factors with EHEC O157:H7, including NleH, we observed that the wild-type strain exhibited a competitive advantage over the mutant during mixed infection. We found no measurable differences in T-cell infiltration or hyperplasia in colons of mice inoculated with the wild-type or the nleH mutant strain. Using NF-κB reporter mice carrying a transgene containing a luciferase reporter driven by three NF-κB response elements, we found that NleH causes an increase in NF-κB activity in the colonic mucosa. Consistent with this, we found that the nleH mutant triggered a significantly lower tumor necrosis factor alpha response than the wild-type strain.
Intestinal colonization by enteropathogenic and enterohemorrhagic Escherichia coli requires the locus of enterocyte effacement-encoded type III secretion system. We report that NleC and NleD are ...translocated into host cells via this system. Deletion mutants induced attaching and effacing lesions in vitro, while infection of calves or lambs showed that neither gene was required for colonization.
The influence of building geometry on the radiation terms of the surface energy balance is a principal reason for surface temperature differences between rural and urban areas. Methods exist to ...calculate the radiation balance in an urban area, but their validity across the range of urban geometries and materials has not been carefully considered. Here the exchange of diffuse radiation in an urban street canyon is investigated using a method incorporating all reflections of radiation. This exact solution is compared to two commonly used approximations that retain either no reflections, or just one reflection of radiation. The area-averaged net radiative flux density from the facets of the canyon decreases in magnitude monotonically as the canyon aspect ratio increases. The two approximate solutions possess unphysical differences from this monotonic decrease for high canyon aspect ratios or low material emissivities/high material albedos. The errors of the two approximate solutions are small for near blackbody materials and small canyon aspect ratios but can be an order of magnitude for intermediate material properties and deep street canyons. Urban street canyon models need to consider at least one reflection of radiation and multiple reflections are desirable for full applicability.
Shiga toxin (Stx)-positive Escherichia coli O157:H7 readily colonize and persist in specific-pathogen-free (SPF) chicks, and we have shown that an Stx-negative E. coli O157:H7 isolate (NCTC12900) ...readily colonizes SPF chicks for up to 169 days after oral inoculation at 1 day of age. However, the role of intimin in the persistent colonization of poultry remains unclear. Thus, to investigate the role of intimin and flagella, which is a known factor in the persistence of non-O157 E. coli in poultry, isogenic single- and double-intimin and aflagellar mutants were constructed in E. coli O157:H7 isolate NCTC12900. These mutants were used to inoculate (10⁵ CFU) 1-day-old SPF chicks. In general, significant attenuation of the aflagellate and intimin-aflagellate mutants, but not the intimin mutant, was noted at similar time points between 22 and 92 days after inoculation. The intimin-deficient mutant was still being shed at the end of the experiment, which was 211 days after inoculation, 84 days more than the wild type. Shedding of the aflagellar and intimin-aflagellar mutants ceased 99 and 113 days after inoculation, respectively. Histological analysis of gastrointestinal tissues from inoculated birds gave no evidence for true microcolony formation by NCTC12900 or intimin and aflagellar mutants to epithelial cells. However, NCTC12900 mutant derivatives associated with the mucosa were observed as individual cells and/or as large aggregates. Association with luminal contents was also noted. These data suggest that O157 organisms do not require intimin for the persistent colonization of chickens, whereas flagella do play a role in this process.
Context.
Radio loud active galactic nuclei (RLAGNs) are often morphologically complex objects that can consist of multiple, spatially separated, components. Only when the spatially separated radio ...components are correctly grouped together can we start to look for the corresponding optical host galaxy and infer physical parameters such as the size and luminosity of the radio object. Existing radio detection software to group these spatially separated components together is either experimental or based on assumptions that do not hold for current generation surveys, such that, in practice, astronomers often rely on visual inspection to resolve radio component association. However, applying visual inspection to all the hundreds of thousands of well-resolved RLAGNs that appear in the images from the Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) at 144 MHz, is a daunting, time-consuming process, even with extensive manpower.
Aims.
Using a machine learning approach, we aim to automate the radio component association of large (>15 arcsec) radio components.
Methods.
We turned the association problem into a classification problem and trained an adapted Fast region-based convolutional neural network to mimic the expert annotations from the first LoTSS data release. We implemented a rotation data augmentation to reduce overfitting and simplify the component association by removing unresolved radio sources that are likely unrelated to the large and bright radio components that we consider using predictions from an existing gradient boosting classifier.
Results.
For large (>15 arcsec) and bright (>10 mJy) radio components in the LoTSS first data release, our model provides the same associations for 85.3% ± 0.6 of the cases as those derived when astronomers perform the association manually. When the association is done through public crowd-sourced efforts, a result similar to that of our model is attained.
Conclusions.
Our method is able to efficiently carry out manual radio-component association for huge radio surveys and can serve as a basis for either automated radio morphology classification or automated optical host identification. This opens up an avenue to study the completeness and reliability of samples of radio sources with extended, complex morphologies.
•In catchments <300 km2 geology controls daily- to multi-year streamflow variability.•Catchments >300 km2 variability mostly from mixing upstream- and downstream-flow.•JULES land surface model ...performs poorly in small, high-permeability catchments.•Diverting some rainfall as bypass flow to bedrock improves JULES simulated flow.
Geological factors controlling daily- to multi-year discharge variability in 48 sub-catchments spanning 10–1000 km2 in the Thames Basin were investigated using cross-spectral analysis. The analyses represent a ‘transfer function approach’ applied to daily observed streamflow (output) versus catchment-wide precipitation (input) for data spanning 1990–2014. Catchments dominated by high-permeability bedrock have significant attenuation of high-frequency precipitation variability and large delays at all frequencies with streamflow dominated by baseflow (high lag1 autocorrelation and high Base Flow Index, BFI). Catchments dominated by low-permeability rocks have little high-frequency attenuation and small delays and consequently ‘flashy’ behaviour. For all sub-catchments >300 km2 in the Thames Basin, attenuation of the highest frequency precipitation variability caused by mixing of flow from upstream plus groundwater flow (representing ‘older’ variability) with direct surface flow (‘younger’ variability) constitutes real-world moving averaging as indicated by a roll-off in power at the highest frequencies.
The success of the JULES land surface model in simulating discharge (i.e. surface and sub-surface runoff routed between grid boxes) is also linked to the underlying geology. Larger catchments (>300 km2) are modelled well because routing between numerous grid boxes leads to moving averaging that is a good analogue for the observations. Modelling was least successful (e.g. lowest Kling-Gupta Efficiency) for small catchments (<300 km2) dominated by high-permeability bedrock - with far too little attenuation of high-frequency precipitation variability and insufficient delays at all frequencies. Experimentally switching the soil saturated hydraulic conductivity to that of the underlying bedrock for grid boxes dominated by aquifers significantly improves modelled discharge variability in small sub-catchments - confirming the importance of bedrock permeability in modelling.
For small catchments in data-sparse regions, knowledge of the relative proportions of different hydrogeological units (aquifers, aquitards) potentially could be used to predict and model discharge variability as characterised by BFI and lag1 autocorrelation.
Abstract The ability of Escherichia coli O157:H7 to colonize the intestinal epithelia is dependent on the expression of intimin and other adhesins. The chromosome of E. coli O157:H7 carries two loci ...encoding long polar fimbriae (LPF). These fimbriae mediate adherence to epithelial cells and are associated with colonization of the intestine. In order to increase our knowledge about the conditions controlling their expression and their role in colonization of an animal model, the environmental cues that promote expression of lpf genes and the role of E. coli O157:H7 LPF in intestinal colonization of lambs were investigated. We found that expression of lpf1 was regulated in response to growth phase, osmolarity, and pH; that lpf2 transcription was stimulated during late exponential growth and iron depletion; and that LPF impacts the ability of E. coli O157:H7 to persist in the intestine of infected 6-week-old lambs.
For the first time, comatulid crinoid feeding behaviour is used to infer near-bottom current (NBC) directions on the Terre Adélie and George V shelf, East Antarctica. We analysed 47 still-image and ...video transects sampled during the Collaborative East Antarctic Marine Census (CEAMARC) expedition in 2007–2008. We recorded the inferred current direction from 1537 comatulid observations and interpolated these data across the shelf using the Natural Neighbour Interpolation (NNI) method. Results revealed a mode current directionality at each station and a close local agreement between the observed and interpolated NBC directions. The interpolated NBC directions show a coherent counter-clockwise gyre in the deep George V Basin, with a northward and westward flow over the northern flank of the basin and eastward flow near the coast, consistent with the distribution of bottom salinity. There also appears to be a clockwise gyre on the relatively shallow Adélie Bank, with an easterly or southeasterly flow along the outer-shelf, south and southwesterly on the east Adélie Bank, and westerly along the Terre Adélie coast.
Inclusion of vegetation is critical for urban land surfacemodels (ULSM)to represent reasonably the turbulent sensible and latent heat flux densities in an urban environment. Here the Joint UK Land ...Environment Simulator (JULES), a ULSM, is used to simulate the Bowen ratio at a number of urban and rural siteswith vegetation cover varying between 1% and 98%. The results show that JULES is able to represent the observed Bowen ratios, but only when the additional anthropogenic water supplied into the urban ecosystem is considered. The impact of the external water use (e.g., through irrigation or street cleaning) on the surface energy flux partitioning can be as substantial as that of the anthropogenic heat flux on the sensible and latent heat fluxes. The Bowen ratio varies from 1 to 2 when the plan area vegetation fraction is between 30% and 70%. However, when the vegetation fraction is less than 20%, the Bowen ratios increase substantially (2–10) and have greater sensitivity to assumptions about external water use. As there are few long-term observational sites with vegetation cover less than 30%, there is a clear need for more measurement studies in such environments.
Intimin and EspA proteins are virulence factors expressed by attaching and effacing
Escherichia coli (AEEC) such as enteropathogenic and enterohaemorrhagic
E. coli. The EspA protein makes up a ...filament structure forming part of the type III secretion system (TTSS) that delivers effector proteins to the host epithelial cell. Bacterial surface displayed intimin interacts with translocated intimin receptor in the host cell membrane leading to intimate attachment of the bacterium and subsequent attaching and effacing lesions. Here, we have assessed the use of recombinant monoclonal antibodies against
E. coli O157:H7 EspA and intimin for the disruption of AEEC interaction with the host cell. Anti-γ intimin antibodies did not reduce either adhesion of
E. coli O157:H7 to host cell mono-layers or subsequent host cell actin rearrangement. Anti-EspA antibodies similarly had no effect on bacterial adhesion however they had a marked effect upon
E. coli O157:H7-induced host cell actin rearrangement, where both monoclonal and polyclonal antibodies completely blocked cytoskeletal changes within the host cell. Furthermore, these anti-EspA antibodies were shown to reduce actin rearrangement induced by some but not all other AEEC serotypes tested. Both polyclonal and monoclonal antibodies could be used to label
E. coli O157 EspA filaments and these immunoreagents did not inhibit the formation of such filaments. This is the first report of monoclonal antibodies to EspA capable of disrupting the TTSS function of
E. coli O157:H7.
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