Surface Exposition Research Articles

Native Oxidation of HgCdTe Compound Semiconductors and Its Impact on Infrared Detectors Performances

HgCdTe surface processing and exposition to the atmospheric environment promote the formation of surface oxides, which have been reported to influence the electrical behavior of devices. This work investigates the formation of HgCdTe of air native oxides on epitaxial Hg(1-x)Cd(x)Te layers after a standard wet etching procedure (x ≃ 0.2 to 0.7). Real-Time Spectroscopic Ellipsometry (RTSE) studies were performed to monitor initial native oxide formation in a clean-room environment and revealed a two-stage kinetic of oxide formation. X-ray Photoelectron Spectroscopy (XPS) was used to assess the evolution of the surface chemistry. After etching, the surfaces exhibited an excess of tellurium that oxidized during early oxide formation (< 45min). Longer air exposures resulted in oxide thicknesses correlated to the alloy composition, indicating a cadmium contribution to further oxidize the material. The combination of techniques allowed the investigation of the formation mechanisms surrounding the native oxide of wet-etched HgCdTe surfaces.

Tailor-made polymer tracers reveal the role of clay minerals on colloidal transport in carbonate media

HypothesisHost rock weathering and incipient pedogenesis result in the exposition of minerals, e.g., clay minerals in sedimentary limestones. Once exposed, these minerals provide the surfaces for fluid–solid interactions that control the fate of dissolved or suspended compounds such as organic matter and colloids. However, the functional and compositional diversity of organic matter and colloids limits the assessment of reactivity and availability of clay mineral interfaces. Such assessment demands a mobile compound with strong affinity to clay surfaces that is alien to the subsurface. ExperimentWe approached this challenge by using poly(ethylene glycol) (PEG) as interfacial tracer in limestone weathering experiments. FindingsPEG adsorption and transport was dependent on the availability of clay mineral surfaces and carbonate dissolution dynamics. In addition, PEG adsorption featured adsorption–desorption hysteresis which retained PEG mass on clay mineral surfaces. This resulted in different PEG transport for experiments conducted consecutively in the same porous medium. As such, PEG transport was reconstructed with a continuum-scale model parametrized by a Langmuir-type isotherm including hysteresis. Thus, we quantified the influence of exposed clay mineral surfaces on the transport of organic colloids in carbonate media. This renders PEG a suitable model colloid tracer for the assessment of clay surface exposition in porous media.

Study of the Role of Lipoprotein Maturation Enzymes in the Pathogenesis of the Infection Caused by the Streptococcus suis Serotype 2 Sequence Type 25 North American Prototype Strain.

Streptococcus suis serotype 2 is an important swine bacterial pathogen causing sudden death, septic shock, and meningitis. However, serotype 2 strains are phenotypically and genotypically heterogeneous and composed of a multitude of sequence types (STs) whose distributions greatly vary worldwide. It has been previously shown that the lipoprotein (LPP) maturation enzymes diacylglyceryl transferase (Lgt) and signal peptidase (Lsp) significantly modulate the inflammatory host response and play a differential role in virulence depending on the genetic background of the strain. Differently from Eurasian ST1/ST7 strains, the capsular polysaccharide of a North American S. suis serotype 2 ST25 representative strain only partially masks sub-capsular domains and bacterial wall components. Thus, our hypothesis is that since LPPs would be more surface exposed in ST25 strains than in their ST1 or ST7 counterparts, the maturation enzymes would play a more important role in the pathogenesis of the infection caused by the North American strain. Using isogenic Δlgt and Δlsp mutants derived from the wild-type ST25 strain, our studies suggest that these enzymes do not seem to play a role in the interaction between S. suis and epithelial and endothelial cells, regardless of the genetics background of the strain used. However, a role in the formation of biofilms (also independently of the STs) has been demonstrated. Moreover, the involvement of LPP dendritic cell activation in vitro seems to be somehow more pronounced with the ST25 strain. Finally, the Lgt enzyme seems to play a more important role in the virulence of the ST25 strain. Although some differences between STs could be observed, our original hypothesis that LPPs would be significantly more important in ST25 strains due to a better bacterial surface exposition could not be confirmed.

The Recruitment and Activation of Plasminogen by Bacteria—The Involvement in Chronic Infection Development

The development of infections caused by pathogenic bacteria is largely related to the specific properties of the bacterial cell surface and extracellular hydrolytic activity. Furthermore, a significant role of hijacking of host proteolytic cascades by pathogens during invasion should not be disregarded during consideration of the mechanisms of bacterial virulence. This is the key factor for the pathogen evasion of the host immune response, tissue damage, and pathogen invasiveness at secondary infection sites after initial penetration through tissue barriers. In this review, the mechanisms of bacterial impact on host plasminogen—the precursor of the important plasma serine proteinase, plasmin—are characterized, principally focusing on cell surface exposition of various proteins, responsible for binding of this host (pro)enzyme and its activators or inhibitors, as well as the fibrinolytic system activation tactics exploited by different bacterial species, not only pathogenic, but also selected harmless residents of the human microbiome. Additionally, the involvement of bacterial factors that modulate the process of plasminogen activation and fibrinolysis during periodontitis is also described, providing a remarkable example of a dual use of this host system in the development of chronic diseases.

The changes of blood platelet reactivity in the presence of Elaeagnus rhamnoides (L.) A. Nelson leaves and twig extract in whole blood

Uncontrolled blood platelet activation is an important risk factor of cardiovascular disease (CVDs). Various studies on phenolic compounds indicate that they have a protective effect on the cardiovascular system through different mechanisms, including the reduction of blood platelet activation. One of the plants that is particularly rich in phenolic compounds is sea buckthorn (Elaeagnus rhamnoides (L.) A. Nelson). The aim of the present study in vitro was to determine the anti-platelet properties of crude extracts isolated from leaves and twigs of E. rhamnoides (L.) A. Nelson in whole blood using flow cytometric and total thrombus-formation analysis system (T-TAS). In addition, the aim of our study was also analyze of blood platelet proteomes in the presence of different sea buckthorn extracts. A significant new finding is a decrease surface exposition of P-selectin on blood platelets stimulated by 10 µM ADP and 10 µg/mL collagen, and a decrease surface exposition of GPIIb/IIIa active complex on non-activated platelets and platelets stimulated by 10 µM ADP and 10 µg/mL collagen in the presence of sea buckthorn leaf extract (especially at the concentration 50 µg/mL). The twig extract also displayed antiplatelet potential. However, this activity was higher in the leaf extract than in the twig extract in whole blood. In addition, our present findings clearly demonstrate that investigated plant extracts have anticoagulant properties (measured by T-TAS). Therefore, the two tested extracts may be promising candidates for the natural anti-platelet and anticoagulant supplements.

Recyclable photocatalytic composites based on natural hydrogels for dye degradation in wastewaters

Two polysaccharide-based hydrogels: agarose and chitosan have been used to shape pieces containing micrometer anatase (TiO2). The degradation of Methylene Blue and Rhodamine, two pigments frequently found in textile industry wastewaters, has been employed to test the photocatalytic capacity of such composites. These experiments were carried out indoor under an artificial light that simulates the solar spectrum. An initial test demonstrated that the agarose-containing pieces showed a degradation superior to that observed when chitosan or chitosan/agarose mixtures were used to aggregate the TiO2 powders. The following parameters: pieces geometry, surface exposition, porosity and anatase content were optimized to reach the highest degradation capability. The so obtained materials, subjected to long term and reutilization studies, showed that high degradation rates were maintained even under such conditions. Taking this into account, it can be stated that these low cost and recyclable pieces have a great potential applicability for actual wastewater depollution procedures.

Modulation of CD36-mediated lipid accumulation and senescence by vitamin E analogs in monocytes and macrophages.

The CD36/FAT scavenger receptor/fatty acids transporter regulates cellular lipid accumulation important for inflammation, atherosclerosis, lipotoxicity, and initiation of cellular senescence. Here we compared the regulatory effects of the vitamin E analogs alpha-tocopherol (αT), alpha-tocopheryl phosphate (αTP), and αTP/βCD (a nanocarrier complex between αTP and β-cyclodextrin [βCD]) and investigated their regulatory effects on lipid accumulation, phagocytosis, and senescence in THP-1 monocytes and macrophages. Both, αTP and αTP/βCD inhibited CD36 surface exposition stronger than αT leading to more pronounced CD36-mediated events such as inhibition of DiI-labeled oxLDL uptake, phagocytosis of fluorescent Staphylococcus aureus bioparticles, and cell proliferation. When compared to βCD, the complex of αTP/βCD extracted cholesterol from cellular membranes with higher efficiency and was associated with the delivery of αTP to the cells. Interestingly, both, αTP and more so αTP/βCD inhibited lysosomal senescence-associated beta-galactosidase (SA-β-gal) activity and increased lysosomal pH, suggesting CD36-mediated uptake into the endo-lysosomal phagocytic compartment. Accordingly, the observed pH increase was more pronounced with αTP/βCD in macrophages whereas no significant increase occurred with αT, alpha-tocopheryl acetate (αTA) or βCD. In contrast to αT and αTA, the αTP molecule is di-anionic at neutral pH, but upon moving into the acidic endo-lysosomal compartment becomes protonated and thus is acting as a base. Moreover, it is expected to be retained in lysosomes since it still carries one negative charge, similar to lysosomotropic drugs. Thus, treatment with αTP or αTP/βCD and/or inhibition of conversion of αTP to αT as it occurs in aged cells may counteract CD36-mediated overlapping inflammatory, senescent, and atherosclerotic events.

Effects of Water on Natural Stone in the Built Environment—A Review

The present work reviews studies with information on the effects of water by itself on stones of the built environment both to assess the impact of this substance and to discuss possible implications for conservation. The analysis concerns empirical results from previous publications dealing with the effects, on several rock types, of freeze–thaw, wetting, erosion by running water and substances resulting from the water–stone interaction. Laboratory studies have shown that water freezing can cause physical damage even in low porosity rocks. As far as we know, this is the first review that considers comparative laboratory studies of freeze–thaw and salt crystallization on the same rock specimens, and these point to lower erosive effects than salt weathering, as freeze–thaw can provoke catastrophic cracking. Wetting has shown strong damaging effects on some fine-grained clastic rocks. Erosive features have been reported for rain exposition and for some fountain settings albeit, in these field studies, it could be difficult to assess the contribution of pollutants transported by water (this assessment could have meaningful implications for stone conservation, especially in fountain settings). Water also interacts with stone constituents, namely sulfides and soluble salts, releasing substances that could impact those stones. Sulfides are a relatively frequent issue for slates and granites, and our observations suggest that for this last rock type, this issue is mostly associated with the presence of enclaves and, hence, avoiding the surface exposition of such enclaves could solve the problem.

Antithrombotic and hemocompatible properties of nanostructured coatings assembled from block copolymers

We describe the antithrombotic properties of nanopatterned coatings created by self-assembly of poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) with different molecular weights. By changing the assembly conditions, we obtained nanopatterns that differ by their morphology (size and shape of the nanopattern) and chemistry. The surface exposition of P2VP block allowed quaternization, i.e. introduction of positive surface charge and following electrostatic deposition of heparin. Proteins (albumin and fibrinogen) adsorption, platelet adhesion and activation, cytocompatibility, and reendothelization capacity of the coatings were assessed and discussed in a function of the nanopattern morphology and chemistry. We found that quaternization results in excellent antithrombotic and hemocompatible properties comparable to heparinization by hampering the fibrinogen adhesion and platelet activation. In the case of quaternization, this effect depends on the size of the polymer blocks, while all heparinized patterns had similar performance showing that heparin surface coverage of 40 % is enough to improve substantially the hemocompatibility.

Modulation of CD36‐mediated Lipid Accumulation and Senescence by Vitamin E Analogues in Monocytes and Macrophages

The CD36/FAT scavenger receptor/fatty acids transporter regulates cellular lipid accumulation important for inflammation, atherosclerosis, lipotoxicity and initiation of cellular senescence. During stress-induced premature senescence (SIPS), a number of stimuli (e.g., oxLDL, β-amyloid and 4-hydroxynonenal) may lead to up-regulation of CD36-mediated lipid uptake triggering signaling and the expression of lipid-regulating and inflammatory genes involved in the senescence-associated secretory phenotype (SASP) characterized by secretion of cytokines, chemokines, lipids and proteases. Both, SIPS and SASP may be modulated by vitamin E (alpha-tocopherol, αT), since it inhibits CD36 expression, cell surface exposition and CD36-associated signaling. Here we compared the regulatory effects of αT, αTP (alpha-tocopheryl phosphate, αTP) and αTP/βCD (a nanocarrier complex between αTP and β-cyclodextrin (βCD)) and investigated their regulatory effects on lipid accumulation, phagocytosis and senescence in THP-1 monocytes and macrophages. Both, αTP and αTP/βCD inhibited CD36 surface exposition stronger that αT leading to more pronounced CD36-mediated events such as inhibition of DiI-labelled oxLDL uptake, phagocytosis of fluorescent Staphylococcus aureus bioparticles, and cell proliferation. When compared to βCD, the complex of αTP/βCD extracted cholesterol from cellular membranes with higher efficiency and was associated with delivery of αTP to the cells, thus forming a Dual-Action Lipid-lowering complex (DALC). Interestingly, both, αTP and more so αTP/βCD inhibited lysosomal senescent-associated beta-galactosidase (SA-β-gal) activity and increased lysosomal pH, suggesting CD36-mediated uptake into the endo-lysosomal phagocytic compartment. Accordingly, the observed pH increase was more pronounced with αTP/βCD in macrophages when compared to monocytes, possibly due to their increased ability to phagocytose the αTP/βCD complex, whereas no significant change of pH occurred with αT, alpha-tocopherol acetate (αTA) or βCD. In contrast to αT and αTA, the αTP molecule is di-anionic at neutral pH (calculated pKa1 1.64 and pKa2 6.07), but upon moving into the acidic endo-lysosomal compartment becomes protonated and thus is acting as a base. Moreover, it is expected to be retained in lysosomes since it still carries one negative charge, as it occurs also with lysosomotropic drugs such as chloroquine and hydroxychloroquine. Thus, treatment with αTP or αTP/βCD and/or inhibition of conversion of αTP to αT as it occurs in aged cells may counteract CD36-mediated overlapping inflammatory, senescent, and atherosclerotic events.

Effects of Sandblasting and Hydrofluoric Acid Etching on Surface Topography, Flexural Strength, Modulus and Bond Strength of Composite Cement to Ceramics.

To evaluate the influence of different surface treatments of two CAD/CAM glass ceramics on surface topography, shear bond strength of composite cement, flexural strength, and elastic modulus. Two ceramics were evaluated: lithium-disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) glass ceramics. Glass ceramics were sintered and the surfaces were sandblasted (SBL) or etched with 9% hydrofluoric acid for 10 s (HF10), 20 s (HF20) or 30 s (HF30). The treated surfaces were analyzed using scanning electron microscopy (n = 3) to evaluate the etching pattern. For bond strength testing, ceramic samples were silanized after treatments and an adhesive was applied to the surface. Afterwards, a silicone mold was used to build composite-cement cylinders, which were tested after 24 h or one year of water storage (n = 10). Flexural strength and modulus were assessed using a 3-point bending test (n = 15). The data were subjected to statistical analysis at a pre-set α = 0.05. SBL and HF resulted in different surface topographies. Increased HF etching time influenced the surface dissolution level and exposition of crystals for LDS, while no effect of etching time was observed for ZLS. After one year, the bond strength to LDS significantly decreased, regardless of treatments. For ZLS, HF10 and HF20 showed stable bond strengths over time. SBL yielded the lowest bond strength for both ceramics and statistically significantly reduced the flexural strength of ZLS. The flexural strength and elastic modulus of ceramics were not affected by different etching times. Bonding stability depended on the glass ceramic and the pretreatment method employed. HF etching did not change the mechanical properties of the ceramics and is indicated as a ceramic treatment for bonding.

Conjugation of Mannans to Enhance the Potency of Liposome Nanoparticles for the Delivery of RNA Vaccines.

Recent approval of mRNA vaccines to combat COVID-19 have highlighted the potential of this platform. Lipid nanoparticles (LNP) is the delivery vehicle of choice for mRNA as they prevent its enzymatic degradation by encapsulation. We have recently shown that surface exposition of mannose, incorporated in LNPs as stable cholesterol-amine conjugate, enhances the potency of self-amplifying RNA (SAM) replicon vaccines through augmented uptake by antigen presenting cells (APCs). Here, we generated a new set of LNPs whose surface was modified with mannans of different length (from mono to tetrasaccharide), in order to study the effect on antibody response of model SAM replicon encoding for the respiratory syncytial virus fusion F protein. Furthermore, the impact of the mannosylated liposomal delivery through intradermal as well as intramuscular routes was investigated. The vaccine priming response showed to improve consistently with increase in the chain length of mannoses; however, the booster dose response plateaued above the length of disaccharide. An increase in levels of IgG1 and IgG2a was observed for mannnosylated lipid nanoparticles (MLNPs) as compared to LNPs. This work confirms the potential of mannosylated SAM LNPs for both intramuscular and intradermal delivery, and highlights a disaccharide length as sufficient to ensure improved immunogenicity compared to the un-glycosylated delivery system.

The HPV and p63 Status in Penile Cancer Are Linked with the Infiltration and Therapeutic Availability of Neutrophils.

Squamous penile cancer displays a rare human papillomavirus (HPV)-associated tumor entity. Investigations on the molecular pathogenesis of HPV-driven penile cancer are impaired by the rareness of clinical specimens and, in particular, are missing relevant cell culture models. Here, we identified in HPV-positive penile cancer cell lines that HPV16 oncoproteins control TP63 expression by modulating critical regulators, while integration into the TP63 open reading frame facilitates oncogene expression. The resulting feed-forward loop leads to elevated p63 levels that in turn enhance the release of the neutrophil-recruiting chemokine CXCL8. Remarkably, elevated CXCL8 amounts lead to the increased surface exposition of the Fc receptor of human IgA antibodies, FcαRI, on neutrophils and correlated with a higher susceptibility to antibody-dependent neutrophil-mediated cytotoxicity (ADCC) using an EGFR-specific IgA2 antibody. IHC staining of tissue microarrays proved that elevated expression of p63 together with neutrophil infiltration were significantly more frequent in HPV-positive penile cancer displaying a higher tumor grade. In summary, we identified a promising marker profile of patients with penile cancer at higher risk for worse prognosis. However, these patients may benefit from immunotherapeutic approaches efficiently engaging neutrophils for tumor cell killing.

Salmonella Typhimurium enolase-like membrane protein is recognized by antibodies against human enolase and interacts with plasminogen.

Enolase is generally known as the glycolytic pathway enzyme present in the cytoplasm of eukaryotic cells and in some microorganisms. In human cells, it is also a component of cell surface membranes, where it functions as a human plasminogen receptor. The study aimed to purify Salmonella enterica serovar Typhimurium cytosolic enolase and obtain the antibodies against this protein; to identify enolase on the surface of bacteria; and to find cross-reactivity and plasminogen binding properties. Cytosolic enolase from S. Typhimurium was purified using a five-step preparation method. Anti-cytosolic enolase antibodies combined with scanning electron microscopy (SEM) allowed us to detect enolase on the surface of intact S. Typhimurium cells. The binding of plasminogen to surface enolase and the cross-reactivity of this protein with antibodies against human enolases were tested with western blot. Antibodies against human α- and β-enolases cross-reacted with S. Typhimurium membrane protein, the identity of which was further confirmed using a mass spectrometry analysis of enolase tryptic peptides. The enolase form bacterial membrane also bound plasminogen. The cross-reactivity of membrane enolase with antibodies against human enolases suggests that this bacterium shares epitopes with human proteins. Surface exposition of enolase and the demonstrated affinity for human plasminogen indicates that Salmonella membrane enolase could play a role in the interaction of S. Typhimurium with host cells.

Functional analysis of glycosylation in Etanercept: Effects over potency and stability

Etanercept is a biotechnological product that has a complex glycosylation profile. To elucidate Etanercept glycosylation effect over biological activity and stability, we deglycosylated sequentially this molecule. Sequential deglycosylation was performed to understand which glycans are critical for Etanercept folding and activity. Extended study showed that gross glycosylation differences, affect thermal stability, hydrodynamic radius, pI, CDC, ADCC, protection against oxidation and charge surface exposition with any effect (within biological assay dispersion) over TNFα neutralization, indicating which glycoforms have a critical effect over Etanercept ADCC, CDC and stability. In this regard, complete remotion of sialic acids have a predominant importance over pI, ADCC, CDC and surface charge while N and O glycosylation over thermal stability, hydrophobicity, aggregation and protection against oxidation. Our research suggest that gross differences in the glycosylation profile are relevant for the stability and biological main activities of Etanercept, and that significant differences that affect the activities related to this fusion protein could be detected with proper analytical methods and stability studies.

Modulation of lipid accumulation in monocytes and macrophages by cyclodextrin‐based nanocarriers for alpha‐tocopheryl phosphate

Vitamin E can modulate the CD36/FAT scavenger receptor/fatty acids transporter activity and affect lipid accumulation in monocytes and macrophages, important events for inflammation, lipotoxicity and foam cells formation during atherosclerosis. Similar to that, cyclodextrins (CD) can sequester and trigger export of lipids and influence cholesterol‐mediated signaling and gene expression leading to macrophages reprogramming and lipid lowering effects in a number of disease models. We have now combined the phosphorylated vitamin E analogue (alpha‐tocopheryl phosphate, αTP) and beta‐cyclodextrin (βCD) in a novel formulation to evaluate its regulatory effects and mechanisms of action on lipid accumulation in human monocytes/macrophages. In human THP‐1 monocytes and macrophages, the αTP/βCD complex not only increased the cellular delivery of αTP, but also reduced lipid accumulation by reducing CD36/FAT surface exposition and/or by enhancing the removal of cholesterol from the cells/membranes. A comparable activity was observed with higher order complexes of αTP/βCD with three types of modified starches or chitosan that may be useful as protective vehicle to increase oral, dermal or ocular delivery, or act as deposit‐enhancer in mucosa for delivery across epithelia. Moreover, preliminary results suggest that the αTP/βCD complex can influence signal transduction and gene expression pathways centrally involved in regulating cellular lipid homeostasis and inflammation. Thus, by acting as a Dual Action Lipid‐lowering Complex (DALC), αTP/βCD may not only increase the delivery of αTP and reduce cellular lipid accumulation by influencing CD36‐mediated signaling and gene expression relevant for lipid homeostasis, inflammation and cellular senescence, but also by stimulating βCD‐mediated lipid removal and macrophage reprogramming. In vivo, similar or better reductions of cellular lipids/cholesterol may be achieved possibly at lower concentrations as result of increased bioavailability and stability of αTP and of enhanced βCD‐mediated lipid exchange and macrophages reprogramming relevant not only for inflammation and atherosclerosis, but also for non‐alcoholic steatohepatitis (NASH), tumorigenesis and Parkinson's Disease.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Tree Density and Forest Productivity in a Heterogeneous Alpine Environment: Insights from Airborne Laser Scanning and Imaging Spectroscopy

We outline an approach combining airborne laser scanning (ALS) and imaging spectroscopy (IS) to quantify and assess patterns of tree density (TD) and forest productivity (FP) in a protected heterogeneous alpine forest in the Swiss National Park (SNP). We use ALS data and a local maxima (LM) approach to predict TD, as well as IS data (Airborne Prism Experiment—APEX) and an empirical model to estimate FP. We investigate the dependency of TD and FP on site related factors, in particular on surface exposition and elevation. Based on reference data (i.e., 1598 trees measured in 35 field plots), we observed an underestimation of ALS-based TD estimates of 40%. Our results suggest a limited sensitivity of the ALS approach to small trees as well as a dependency of TD estimates on canopy heterogeneity, structure, and species composition. We found a weak to moderate relationship between surface elevation and TD (R2 = 0.18–0.69) and a less pronounced trend with FP (R2 = 0.0–0.56), suggesting that both variables depend on gradients of resource availability. Further to the limitations faced in the sensitivity of the applied approaches, we conclude that the combined application of ALS and IS data was convenient for estimating tree density and mapping FP in north-facing forested areas, however, the accuracy was lower in south-facing forested areas covered with multi-stemmed trees.

Characterization of the Porphyromonas gingivalis Type IX Secretion Trans-envelope PorKLMNP Core Complex

The transport of proteins at the cell surface of Bacteroidetes depends on a secretory apparatus known as type IX secretion system (T9SS). This machine is responsible for the cell surface exposition of various proteins, such as adhesins, required for gliding motility in Flavobacterium, S-layer components in Tannerella forsythia, and tooth tissue-degrading enzymes in the oral pathogen Porphyromonas gingivalis Although a number of subunits of the T9SS have been identified, we lack details on the architecture of this secretion apparatus. Here we provide evidence that five of the genes encoding the core complex of the T9SS are co-transcribed and that the gene products are distributed in the cell envelope. Protein-protein interaction studies then revealed that these proteins oligomerize and interact through a dense network of contacts.

The PorX Response Regulator of the Porphyromonas gingivalis PorXY Two-Component System Does Not Directly Regulate the Type IX Secretion Genes but Binds the PorL Subunit.

The Type IX secretion system (T9SS) is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion or cell surface exposition of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY, and PorX encode typical two-component system (TCS) sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN, and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we demonstrate that PorX does not bind T9SS gene promoters and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS.

Local-scale flood mapping on vegetated floodplains from radiometrically calibrated airborne LiDAR data

Knowledge about the magnitude of localised flooding of riverine areas is crucial for appropriate land management and administration at regional and local levels. However, detection and delineation of localised flooding with remote sensing techniques are often hampered on floodplains by the presence of herbaceous vegetation. To address this problem, this study presents the application of full-waveform airborne laser scanning (ALS) data for detection of floodwater extent. In general, water surfaces are characterised by low values of backscattered energy due to water absorption of the infrared laser shots, but the exact strength of the recorded laser pulse depends on the area covered by the targets located within a laser pulse footprint area. To account for this we analysed the physical quantity of radiometrically calibrated ALS data, the backscattering coefficient, in relation to water and vegetation coverage within a single laser footprint. The results showed that the backscatter was negatively correlated to water coverage, and that of the three distinguished classes of water coverage (low, medium, and high) only the class with the largest extent of water cover (>70%) had relatively distinct characteristics that can be used for classification of water surfaces. Following the laser footprint analysis, three classifiers, namely AdaBoost with Decision Tree, Naïve Bayes and Random Forest, were utilised to classify laser points into flooded and non-flooded classes and to derive the map of flooding extent. The performance of the classifiers is highly dependent on the set of laser points features used. Best performance was achieved by combining radiometric and geometric laser point features. The accuracy of flooding maps based solely on radiometric features resulted in overall accuracies of up to 70% and was limited due to the overlap of the backscattering coefficient values between water and other land cover classes. Our point-based classification methods assure a high mapping accuracy (∼89%) and demonstrate the potential of using full-waveform ALS data to detect water surfaces on floodplain areas with limited water surface exposition through the vegetation canopy.