SxsA, a novel surface protein mediating cell aggregation and adhesive biofilm formation of Staphylococcus xylosus

Biofilm formation of staphylococci has been an emerging field of research for many years. However, the underlying molecular mechanisms are still not fully understood and vary widely between species and strains. The aim of this study was to identify new effectors impacting biofilm formation of two Staphylococcus xylosus strains. We identified a novel surface protein conferring cell aggregation, adherence to abiotic surfaces, and biofilm formation. The S. xylosus surface protein A (SxsA) is a large protein occurring in variable sizes. It lacks sequence similarity to other staphylococcal surface proteins but shows similar structural domain organization and functional features. Upon deletion of sxsA, adherence of S. xylosus strain TMW 2.1523 to abiotic surfaces was completely abolished and significantly reduced in TMW 2.1023. Macro- and microscopic aggregation assays further showed that TMW 2.1523 sxsA mutants exhibit reduced cell aggregation compared with the wildtype. Comparative genomic analysis revealed that sxsA is part of the core genome of S. xylosus, Staphylococcus paraxylosus, and Staphylococcus nepalensis and additionally encoded in a small group of Staphylococcus cohnii and Staphylococcus saprophyticus strains. This study provides insights into protein-mediated biofilm formation of S. xylosus and identifies a new cell wall-associated protein influencing cell aggregation and biofilm formation.Peer Reviewe

The ciliate protist tetrahymena pyriformis as a cellular adhesion model for the pathogenic bacterium staphylococcus aureus

Staphylococcus aureus is one of the main pathogenic agents responsible for nosocomial and community-acquired bacterial infections. The pathogenicity of this Gram-positive bacterium is ensured by its different adhesion factors. Collagen and the extracellular glycoprotein adhesin are among the Staphylococcus most important virulence factors. It has been shown that most of the S. aureus strains carry the ica operon, responsible for biofilm production. However, the coexpression of the icaA and the icaD genes is necessary for complete biofilm synthesis. The aim of our study was to study a collection of 15 clinical strains of S. aureus from different sources for the presence of cna and icaD genes coding intercellular adhesion proteins. We also intended to estimate the strains¿ ability to form biofilms by the red Cong method and to test the adhesion ability of S. aureus to the ciliated protist Tetrahymena pyriformis, which we used as a novel cellular adhesion model. Finally, we checked the adhesion¿s inhibition capacity of some plants extracts. The molecular detection of adhesion genes revealed that 80% of strains are cna positive, and 73% are icaD positive. Qualitative biofilm production of S. aureus revealed that 66.6% of strains were slime producers. The adhesion test revealed that 20% of strains are strongly adhering to T. pyriformis and that the Clematis cirrhosa extract has an anti-adhering effect of S. aureus to the ciliate T. pyriformis

NASA Langley Research Center Systems Analysis & Concepts Directorate Participation in the Exploration Systems Architecture Study

The NASA Langley Research Center (LaRC) Systems Analysis & Concepts Directorate (SACD) began studying human exploration missions beyond low Earth orbit (LEO) in the year 1999. This included participation in NASA s Decadal Planning Team (DPT), the NASA Exploration Team (NExT), Space Architect studies and Revolutionary Aerospace Systems Concepts (RASC) architecture studies that were used in formulating the new Vision for Space Exploration. In May of 2005, NASA initiated the Exploration Systems Architecture Study (ESAS). The primary outputs of the ESAS activity were concepts and functional requirements for the Crewed Exploration Vehicle (CEV), its supporting launch vehicle infrastructure and identification of supporting technology requirements and investments. An exploration systems analysis capability has evolved to support these functions in the past and continues to evolve to support anticipated future needs. SACD had significant roles in supporting the ESAS study team. SACD personnel performed the liaison function between the ESAS team and the Shuttle/Station Configuration Options Team (S/SCOT), an agency-wide team charged with using the Space Shuttle to complete the International Space Station (ISS) by the end of Fiscal Year (FY) 2010. The most significant of the identified issues involved the ability of the Space Shuttle system to achieve the desired number of flights in the proposed time frame. SACD with support from the Kennedy Space Center performed analysis showing that, without significant investments in improving the shuttle processing flow, that there was almost no possibility of completing the 28-flight sequence by the end of 2010. SACD performed numerous Lunar Surface Access Module (LSAM) trades to define top level element requirements and establish architecture propellant needs. Configuration trades were conducted to determine the impact of varying degrees of segmentation of the living capabilities of the combined descent stage, ascent stage, and other elements. The technology assessment process was developed and implemented by SACD as the ESAS architecture was refined. SACD implemented a rigorous and objective process which included (a) establishing architectural functional needs, (b) collection, synthesis and mapping of technology data, and (c) performing an objective decision analysis resulting in technology development investment recommendations. The investment recommendation provided budget, schedule, and center/program allocations to develop required technologies for the exploration architecture, as well as the identification of other investment opportunities to maximize performance and flexibility while minimizing cost and risk. A summary of the trades performed and methods utilized by SACD for the Exploration Systems Mission Directorate (ESAS) activity is presented along with how SACD is currently supporting the implementation of the Vision for Space Exploration

Mobility management across converged IP-based heterogeneous access networks

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 8/2/2010.In order to satisfy customer demand for a high performance “global” mobility service, network operators (ISPs, carriers, mobile operators, etc.) are facing the need to evolve to a converged “all-IP” centric heterogeneous access infrastructure. However, the integration of such heterogeneous access networks (e.g. 802.11, 802.16e, UMTS etc) brings major mobility issues. This thesis tackles issues plaguing existing mobility management solutions in converged IP-based heterogeneous networks. In order to do so, the thesis firstly proposes a cross-layer mechanism using the upcoming IEEE802.21 MIH services to make intelligent and optimized handovers. In this respect, FMIPv6 is integrated with the IEEE802.21 mechanism to provide seamless mobility during the overall handover process. The proposed solution is then applied in a simulated vehicular environment to optimize the NEMO handover process. It is shown through analysis and simulations of the signalling process that the overall expected handover (both L2 and L3) latency in FMIPv6 can be reduced by the proposed mechanism by 69%. Secondly, it is expected that the operator of a Next Generation Network will provide mobility as a service that will generate significant revenues. As a result, dynamic service bootstrapping and authorization mechanisms must be in place to efficiently deploy a mobility service (without static provisioning), which will allow only legitimate users to access the service. A GNU Linux based test-bed has been implemented to demonstrate this. The experiments presented show the handover performance of the secured FMIPv6 over the implemented test-bed compared to plain FMIPv6 and MIPv6 by providing quantitative measurements and results on the quality of experience perceived by the users of IPv6 multimedia applications. The results show the inclusion of the additional signalling of the proposed architecture for the purpose of authorization and bootstrapping (i.e. key distribution using HOKEY) has no adverse effect on the overall handover process. Also, using a formal security analysis tool, it is shown that the proposed mechanism is safe/secure from the induced security threats. Lastly, a novel IEEE802.21 assisted EAP based re-authentication scheme over a service authorization and bootstrapping framework is presented. AAA based authentication mechanisms like EAP incur signalling overheads due to large RTTs. As a result, overall handover latency also increases. Therefore, a fast re-authentication scheme is presented which utilizes IEEE802.21 MIH services to minimize the EAP authentication process delays and as a result reduce the overall handover latency. Analysis of the signalling process based on analytical results shows that the overall handover latency for mobility protocols will be approximately reduced by 70% by the proposed scheme

Suitability of foramen magnum measurements in sex determination and their clinical significance

Background: The foramen magnum provides a transition between fossa cranii posterior and canalis vertebralis. Medulla oblongata, arteria vertebralis and nervus accessorius spinal part pass through the foramen magnum. In this study, we aimed to make the morphometric measurements of the foramen magnum on computed tomography (CT) and to determine the feasibility of sex determination based on these measurements. Besides sex determination, from a clinical aspect, it is important to know the measurements of the foramen magnum in the normal population in terms of diseases characterised by displacement of the posterior fossa structures through foramen magnum to upper cervical spinal canal such as Chiari malformations and syringomyelia. Materials and methods: All the data for our study was obtained retrospectively from 100 patients (50 males, 50 females) who had a CT scan of the head and neck region in Adnan Menderes University Hospital, Department of Radiology. To examine the foramen magnum in each and every occipital bone, we measured the foramen magnum’s anteroposterior diameter, transverse diameter, the area of the foramen magnum and its circumference. Results: We found that men have a higher average value than women in our study. According to Student’s t-test results; in all measured parameters, there is significant difference between the genders (p < 0.05). When multivariate discriminant function test is performed for all four measurements, the discrimination rate is 64% for all women, 70% for all men and 67% for both genders. Conclusions: As a result of our study, the metric data we obtained will be useful in cases where the skeletons’ sex could not be determined by any other methods. We believe that, our study may be useful for other studies in determining of sex from foramen magnum. Our measurements could give some information of the normal ranges of the foramen magnum in normal population, so that this can contribute to the diagnosis process of some diseases by imaging. (Folia Morphol 2018; 77, 1: 99–104)  

Validation of the repetitive and restricted behaviour scale in autism spectrum disorders

Repetitive and restricted behaviours represent a common problem for various psychiatric syndromes, especially in autistic spectrum disorders, and they include a wide range of heterogeneous behavioural manifestations. An accurate and standardized description of these behaviours is needed to advance the understanding of this complex and heterogeneous clinical dimension of autism. The present article reports the reliability and validity studies of a new assessment scale: the repetitive and restricted behaviour scale. 145 subjects with autism spectrum disorders were assessed using the RRB scale. The RRB scale has good interrater reliability, internal consistency and content validity. Factorial analysis produced four clinically meaningful factors, i.e. “sensorimotor stereotypies”, “reaction to change”, “restricted behaviours” and “modulation insufficiency”. The RRB scale has good psychometric qualities and constitutes a real breakthrough towards a neurofunctional approach to autistic disorders. It should be valuable for research and treatment, and in clinical practice

Needs analysis and the design of courses in English for academic purposes : a study of the use of English language at the University of Qatar.

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