Spo0J and SMC are required for normal chromosome segregation in Staphylococcus aureus

Bacterial chromosome segregation is an essential cellular process that is particularly elusive in spherical bacteria such as the opportunistic human pathogen Staphylococcus aureus. In this study, we examined the functional significance of a ParB homologue, Spo0J, in staphylococcal chromosome segregation and investigated the role of the structural maintenance of chromosomes (SMC) bacterial condensin in this process. We show that neither spo0J nor smc is essential in S. aureus; however, their absence causes abnormal chromosome segregation. We demonstrate that formation of complexes containing Spo0J and SMC is required for efficient S. aureus chromosome segregation and that SMC localization is dependent on Spo0J. Furthermore, we found that cell division and cell cycle progression are unaffected by the absence of spo0J or smc. Our results verify the role of Spo0J and SMC in ensuring accurate staphylococcal chromosome segregation and also imply functional redundancy or the involvement of additional mechanisms that might contribute to faithful chromosome inheritance

Characterisation of a plasmid segregational stability determinant, par, of the staphylococcal multiresistance plasmid, pSK1

Staphylococcus aureus is a bacterium that is a common cause of hospital-acquired infections that is also becoming a significant cause of serious community-acquired infections. Many clinical strains of S. aureus carry extrachromosomal DNA elements called plasmids, which often encode genes conferring antimicrobial resistance. Plasmid segregation mechanisms such as active partitioning systems ensure that low copy-number plasmids are accurately segregated and inherited by progeny cells upon division, even in the absence of selection. The staphylococcal multiresistance plasmid, pSK1, contains a gene, par, which enhances the efficiency of plasmid inheritance, possibly via an active plasmid partitioning system. Active plasmid partitioning systems characterised thus far encode two individual proteins – a DNA-binding protein and a force-generating NTPase protein. Although the pSK1 par system is widespread among non-conjugative staphylococcal plasmids, it differs from characterised plasmid partitioning systems by encoding only a single protein, Par. Previous studies have shown that pSK1 Par exhibits both DNA-binding and multimerisation activities that are common to characterised partitioning proteins. Much remains to be elucidated about the mechanism by which pSK1 par facilitates efficient plasmid inheritance. This knowledge gap will be addressed by this experiments described in this thesis, which aim to 1) determine the functional significance the predicted Par domains, particularly the disordered C-terminal domain, 2) identify any host factors that interact with Par, and 3) determine the localisation of Par and plasmid DNA during plasmid segregation in S. aureus. These experiments are designed to provide a broader understanding of the mechanism of par-mediated plasmid inheritance, and provide greater insight into possible methods of disrupting the spread and maintenance of antimicrobial resistance plasmids

U.S. Department of Energy Hydrogen Storage Cost Analysis

The overall objective of this project is to conduct cost analyses and estimate costs for on- and off-board hydrogen storage technologies under development by the U.S. Department of Energy (DOE) on a consistent, independent basis. This can help guide DOE and stakeholders toward the most-promising research, development and commercialization pathways for hydrogen-fueled vehicles. A specific focus of the project is to estimate hydrogen storage system cost in high-volume production scenarios relative to the DOE target that was in place when this cost analysis was initiated. This report and its results reflect work conducted by TIAX between 2004 and 2012, including recent refinements and updates. The report provides a system-level evaluation of costs and performance for four broad categories of on-board hydrogen storage: (1) reversible on-board metal hydrides (e.g., magnesium hydride, sodium alanate); (2) regenerable off-board chemical hydrogen storage materials(e.g., hydrolysis of sodium borohydride, ammonia borane); (3) high surface area sorbents (e.g., carbon-based materials); and 4) advanced physical storage (e.g., 700-bar compressed, cryo-compressed and liquid hydrogen). Additionally, the off-board efficiency and processing costs of several hydrogen storage systems were evaluated and reported, including: (1) liquid carrier, (2) sodium borohydride, (3) ammonia borane, and (4) magnesium hydride. TIAX applied a âÂÂbottom-upâ costing methodology customized to analyze and quantify the processes used in the manufacture of hydrogen storage systems. This methodology, used in conjunction with DFMAî software and other tools, developed costs for all major tank components, balance-of-tank, tank assembly, and system assembly. Based on this methodology, the figure below shows the projected on-board high-volume factory costs of the various analyzed hydrogen storage systems, as designed. Reductions in the key cost drivers may bring hydrogen storage system costs closer to this DOE target. In general, tank costs are the largest component of system cost, responsible for at least 30 percent of total system cost, in all but two of the 12 systems. Purchased BOP cost also drives system cost, accounting for 10 to 50 percent of total system cost across the various storage systems. Potential improvements in these cost drivers for all storage systems may come from new manufacturing processes and higher production volumes for BOP components. In addition, advances in the production of storage media may help drive down overall costs for the sodium alanate, SBH, LCH2, MOF, and AX-21 systems

Application of nanotags and nanobodies for live cell single-molecule imaging of the Z-ring in Escherichia coli

Understanding where proteins are localized in a bacterial cell is essential for understanding their function and regulation. This is particularly important for proteins that are involved in cell division, which localize at the division septum and assemble into highly regulated complexes. Current knowledge of these complexes has been greatly facilitated by super-resolution imaging using fluorescent protein fusions. Herein, we demonstrate with FtsZ that single-molecule PALM images can be obtained in-vivo using a genetically fused nanotag (ALFA), and a corresponding nanobody fused to mEos3.2. The methodology presented is applicable to other bacterial proteins.journal articl

A LITERATURE ANALYSIS ABOUT SOCIAL INFORMATION CONTRIBUTION AND CONSUMPTION ON SOCIAL NETWORKING SITES

Social networking sites (SNSs) have emerged as a center for daily social interactions. Every day, millions of users contribute information about themselves, and consume information about others on SNSs. In recent years, we have witnessed a growing number of studies on the issue of social information contribution and consumption behaviors on SNSs. This paper aims to provide a systematic literature review on this topic across different disciplines to understand the current research state and shed light on controversial findings of SNS usage regarding users’ well-being. We identified 126 relevant articles published between 2008 and 2014, and provide an overview of their antecedents and associated outcomes. Our analysis reveals that a majority of existing work focused primarily on social information contribution, its antecedents and favorable outcomes. Only few studies have dealt with contribution behavior and the dark sides of SNS use. Nevertheless, we could identify different characteristics of social information determining the favorability of contribution behavior. Further, we categorized the scarce papers of consumption behavior regarding the social information characteristics and identified different underlying processes: social comparison, monitoring and browsing. These findings contribute to the Information Systems (IS) discipline by consolidating previous knowledge about SNS usage patterns and individual well-being

Humor Therapy: Relieving Chronic Pain and Enhancing Happiness for Older Adults

The present study examined the effectiveness of a humor therapy program in relieving chronic pain, enhancing happiness and life satisfaction, and reducing loneliness among older persons with chronic pain. It was a quasiexperimental pretest-posttest controlled design. Older persons in a nursing home were invited to join an 8-week humor therapy program (experimental group), while those in another nursing home were treated as a control group and were not offered the program. There were 36 older people in the experimental group and 34 in the control group. Upon completion of the humor therapy program, there were significant decreases in pain and perception of loneliness, and significant increases in happiness and life satisfaction for the experimental group, but not for the control group. The use of humor therapy appears to be an effective nonpharmacological intervention. Nurses and other healthcare professionals could incorporate humor in caring for their patients

Cell shape-independent FtsZ dynamics in synthetically remodeled bacterial cells

FtsZ is the main regulator of bacterial cell division. It has been implicated in acting as a scaffolding protein for other division proteins, a force generator during constriction, and more recently, as an active regulator of septal cell wall production. FtsZ assembles into a heterogeneous structure coined the Z-ring due to its resemblance to a ring confined by the midcell geometry. Here, to establish a framework for examining geometrical influences on proper Z-ring assembly and dynamics, we sculpted Escherichia coli cells into unnatural shapes using division- and cell wall-specific inhibitors in a micro-fabrication scheme. This approach allowed us to examine FtsZ behavior in engineered Z-squares and Z-hearts. We use stimulated emission depletion (STED) nanoscopy to show that FtsZ clusters in sculpted cells maintain the same dimensions as their wild-type counterparts. Based on our results, we propose that the underlying membrane geometry is not a deciding factor for FtsZ cluster maintenance and dynamics in vivo

BioNano genome mapping of individual chromosomes supports physical mapping and sequence assembly in complex plant genomes

The assembly of a reference genome sequence of bread wheat is challenging due to its specific features such as the genome size of 17 Gbp, polyploid nature and prevalence of repetitive sequences. BAC-by-BAC sequencing based on chromosomal physical maps, adopted by the International Wheat Genome Sequencing Consortium as the key strategy, reduces problems caused by the genome complexity and polyploidy, but the repeat content still hampers the sequence assembly. Availability of a high-resolution genomic map to guide sequence scaffolding and validate physical map and sequence assemblies would be highly beneficial to obtaining an accurate and complete genome sequence. Here, we chose the short arm of chromosome 7D (7DS) as a model to demonstrate for the first time that it is possible to couple chromosome flow sorting with genome mapping in nanochannel arrays and create a de novo genome map of a wheat chromosome. We constructed a high-resolution chromosome map composed of 371 contigs with an N50 of 1.3 Mb. Long DNA molecules achieved by our approach facilitated chromosome-scale analysis of repetitive sequences and revealed a ~800-kb array of tandem repeats intractable to current DNA sequencing technologies. Anchoring 7DS sequence assemblies obtained by clone-by-clone sequencing to the 7DS genome map provided a valuable tool to improve the BAC-contig physical map and validate sequence assembly on a chromosome-arm scale. Our results indicate that creating genome maps for the whole wheat genome in a chromosome-by-chromosome manner is feasible and that they will be an affordable tool to support the production of improved pseudomolecules

Sample extraction and injection with a microscale preconcentrator.

This report details the development of a microfabricated preconcentrator that functions as a fully integrated chemical extractor-injector for a microscale gas chromatograph (GC). The device enables parts-per-billion detection and quantitative analysis of volatile organic compounds (VOCs) in indoor air with size and power advantages over macro-scale systems. The 44 mm{sup 3} preconcentrator extracts VOCs using highly adsorptive, granular forms of graphitized carbon black and carbon molecular sieves. The micron-sized silicon cavities have integrated heating and temperature sensing allowing low power, yet rapid heating to thermally desorb the collected VOCs (GC injection). The keys to device construction are a new adsorbent-solvent filling technique and solvent-tolerant wafer-level silicon-gold eutectic bonding technology. The product is the first granular adsorbent preconcentrator integrated at the wafer level. Other advantages include exhaustive VOC extraction and injection peak widths an order of magnitude narrower than predecessor prototypes. A mass transfer model, the first for any microscale preconcentrator, is developed to describe both adsorption and desorption behaviors. The physically intuitive model uses implicit and explicit finite differences to numerically solve the required partial differential equations. The model is applied to the adsorption and desorption of decane at various concentrations to extract Langmuir adsorption isotherm parameters from effluent curve measurements where properties are unknown a priori