Surface proteins that promote adherence of Staphylococcus aureus to human desquamated nasal epithelial cells

<p>Abstract</p> <p>Background</p> <p>The natural habitat of <it>Staphylococcus aureus </it>is the moist squamous epithelium in the anterior nares. About 20% of the human population carry <it>S. aureus </it>permanently in their noses and another 60% of individuals are intermittent carriers. The ability of <it>S. aureus </it>to colonize the nasal epithelium is in part due to expression of surface proteins clumping factor B (ClfB) and the iron-regulated surface determinant A (IsdA), which promote adhesion to desquamated epithelial cells present in the anterior part of the nasal vestibule. <it>S. aureus </it>strain Newman defective in IsdA and ClfB exhibited reduced but not completely defective adherence to squamous cells in indicating that other cell surface components might also contribute.</p> <p>Results</p> <p>Surface proteins IsdA, ClfB, and the serine-aspartic acid repeat proteins SdrC, SdrD and SdrE were investigated to determine their contribution to the adherence of <it>S. aureus </it>to desquamated nasal epithelial cells. This was achieved by expression of ClfB, IsdA, SdrC, SdrD and SdrE on the surface of the surrogate Gram-positive host <it>Lactococcus lactis </it>and by isolating mutants of <it>S. aureus </it>Newman defective in one or more factor. The level of adherence of strains to squamous cells isolated from the nares of volunteers was measured. Results consistently showed that ClfB, IsdA, SdrC and SdrD each contributed to the ability of <it>S. aureus </it>to adhere to squamous cells. A mutant lacking all four proteins was completely defective in adherence.</p> <p>Conclusion</p> <p>The ability of <it>S. aureus </it>Newman to adhere to desquamated nasal epithelial cells is multifactorial and involves SdrD and SdrC as well as ClfB and IsdA.</p

Cyanophage MazG is a pyrophosphohydrolase but unable to hydrolyse magic spot nucleotides

Bacteriophage possess a variety of auxiliary metabolic genes (AMGs) of bacterial origin. These proteins enable them to maximise infection efficiency, subverting bacterial metabolic processes for the purpose of viral genome replication and synthesis of the next generation of virion progeny. Here, we examined the enzymatic activity of a cyanophage MazG protein – a putative pyrophosphohydrolase previously implicated in regulation of the stringent response via reducing levels of the central alarmone molecule (p)ppGpp. We demonstrate however, that the purified viral MazG shows no binding or hydrolysis activity against (p)ppGpp. Instead, dGTP and dCTP appear to be the preferred substrates of this protein, consistent with a role preferentially hydrolysing deoxyribonucleotides from the high GC content host Synechococcus genome. This showcases a new example of the fine‐tuned nature of viral metabolic processes

The immune evasion protein Sbi of Staphylococcus aureus occurs both extracellularly and anchored to the cell envelope by binding lipoteichoic acid

The Sbi protein of Staphylococcus aureus comprises two IgG-binding domains similar to those of protein A and a region that triggers the activation of complement C3. Sbi is expressed on the cell surface but its C-terminal domain lacks motifs associated with wall or membrane anchoring of proteins in Gram-positive bacteria. Cell-associated Sbi fractionates with the cytoplasmic membrane and is not solubilized during protoplast formation. S. aureus expressing Sbi truncates of the C-terminal Y domain allowed identification of residues that are required for association of Sbi with the membrane. Recombinant Sbi bound to purified cytoplasmic membrane material in vitro and to purified lipoteichoic acid. This explains how Sbi partitions with the membrane in fractionation experiments yet is partially exposed on the cell surface. An LTA-defective mutant of S. aureus had reduced levels of Sbi in the cytoplasmic membrane

Cross-talk between two nucleotide-signaling pathways in Staphylococcus aureus.

Nucleotide-signaling pathways are found in all kingdoms of life and are utilized to coordinate a rapid response to external stimuli. The stringent response alarmones guanosine tetra- (ppGpp) and pentaphosphate (pppGpp) control a global response allowing cells to adapt to starvation conditions such as amino acid depletion. One more recently discovered signaling nucleotide is the secondary messenger cyclic diadenosine monophosphate (c-di-AMP). Here, we demonstrate that this signaling nucleotide is essential for the growth of Staphylococcus aureus, and its increased production during late growth phases indicates that c-di-AMP controls processes that are important for the survival of cells in stationary phase. By examining the transcriptional profile of cells with high levels of c-di-AMP, we reveal a significant overlap with a stringent response transcription signature. Examination of the intracellular nucleotide levels under stress conditions provides further evidence that high levels of c-di-AMP lead to an activation of the stringent response through a RelA/SpoT homologue (RSH) enzyme-dependent increase in the (p)ppGpp levels. This activation is shown to be indirect as c-di-AMP does not interact directly with the RSH protein. Our data extend this interconnection further by showing that the S. aureus c-di-AMP phosphodiesterase enzyme GdpP is inhibited in a dose-dependent manner by ppGpp, which itself is not a substrate for this enzyme. Altogether, these findings add a new layer of complexity to our understanding of nucleotide signaling in bacteria as they highlight intricate interconnections between different nucleotide-signaling networks

Filmmaking education and enterprise culture: an ethnographic exploration of two filmmaking education contexts and their relation to bedroom culture and the creative workplace

Filmmaking education has never been firmly integrated into schooling and in past years has suffered from cuts to funding for youth work and formal and non-formal arts education. It continues to exist only by drawing on creative industry and cultural consumption practices as well as state funding. In this paper we explore the filmmaking education contexts we encountered while doing our own pieces of year-long ethnographic research. These contexts import 'enterprising' ways of thinking, doing and being from the creative workplace and 'bedroom culture'. Located across life's domains, they address enterprising subjects who take pleasure in work, make use of leisure, and who are always learning. We argue that these filmmaking education contexts support young people to develop their private creative practice and introduce them to the possibility of work in the creative industries but, because of the enterprise culture in which they are entangled, uncritically address these young people as enterprising subjects

Magnetic Flux Density Sensor Analysis

Undergraduate Basi

Safety and anti-tumour activity of the IgE antibody MOv18 in patients with advanced solid tumours expressing folate receptor-alpha: a phase I trial

All antibodies approved for cancer therapy are monoclonal IgGs but the biology of IgE, supported by comparative preclinical data, offers the potential for enhanced effector cell potency. Here we report a Phase I dose escalation trial (NCT02546921) with the primary objective of exploring the safety and tolerability of MOv18 IgE, a chimeric first-in-class IgE antibody, in patients with tumours expressing the relevant antigen, folate receptor-alpha. The trial incorporated skin prick and basophil activation tests (BAT) to select patients at lowest risk of allergic toxicity. Secondary objectives were exploration of anti-tumour activity, recommended Phase II dose, and pharmacokinetics. Dose escalation ranged from 70 μg–12 mg. The most common toxicity of MOv18 IgE is transient urticaria. A single patient experienced anaphylaxis, likely explained by detection of circulating basophils at baseline that could be activated by MOv18 IgE. The BAT assay was used to avoid enrolling further patients with reactive basophils. The safety profile is tolerable and maximum tolerated dose has not been reached, with evidence of anti-tumour activity observed in a patient with ovarian cancer. These results demonstrate the potential of IgE therapy for cancer

Mutation discovery in mice by whole exome sequencing

We report the development and optimization of reagents for in-solution, hybridization-based capture of the mouse exome. By validating this approach in a multiple inbred strains and in novel mutant strains, we show that whole exome sequencing is a robust approach for discovery of putative mutations, irrespective of strain background. We found strong candidate mutations for the majority of mutant exomes sequenced, including new models of orofacial clefting, urogenital dysmorphology, kyphosis and autoimmune hepatitis