Commensal bacteria augment Staphylococcus aureus infection by inactivation of phagocyte-derived reactive oxygen species

Staphylococcus aureus is a human commensal organism and opportunist pathogen, causing potentially fatal disease. The presence of non-pathogenic microflora or their components, at the point of infection, dramatically increases S. aureus pathogenicity, a process termed augmentation. Augmentation is associated with macrophage interaction but by a hitherto unknown mechanism. Here, we demonstrate a breadth of cross-kingdom microorganisms can augment S. aureus disease and that pathogenesis of Enterococcus faecalis can also be augmented. Co-administration of augmenting material also forms an efficacious vaccine model for S. aureus. In vitro, augmenting material protects S. aureus directly from reactive oxygen species (ROS), which correlates with in vivo studies where augmentation restores full virulence to the ROS-susceptible, attenuated mutant katA ahpC. At the cellular level, augmentation increases bacterial survival within macrophages via amelioration of ROS, leading to proliferation and escape. We have defined the molecular basis for augmentation that represents an important aspect of the initiation of infection.     

Production of tailor-made fructans in sugar beet by expression of onion fructosyltransferase genes

The consumption of fructans as a low caloric food ingredient or dietary fibre is rapidly increasing due to health benefits. Presently, the most important fructan source is chicory, but these fructans have a simple linear structure and are prone to degradation. Additional sources of high-quality tailor-made fructans would provide novel opportunities for their use as food ingredients. Sugar beet is a highly productive crop that does not normally synthesize fructans. We have introduced specific onion fructosyltransferases into sugar beet. This resulted in an efficient conversion of sucrose into complex, onion-type fructans, without the loss of storage carbohydrate content.     

NMR of Redox Proteins of Plants, Yeasts and Photosynthetic Bacteria

NMR spectroscopy has evolved dramatically over the past 15 years, establishing a new, reliable methodology for studying biomacromolecules at atomic resolution. The three-dimensional structure and dynamics of a biomolecule or a biomolecular complex is only one of the main types of information available using NMR. The spectral assignment to the specific nuclei of a biostructure is a very precise reflection of their electronic environment. Any change in this environment due to a structural change, the binding of a ligand or the redox state of a redox cofactor, will be very sensitively reported by changes in the different NMR parameters. The capabilities of the NMR method are currently expanding dramatically and it is turning into a powerful means to study biosystems dynamically in exchange between different conformations, exchanging ligands, transient complexes, or the activation/inhibition of regulated enzymes. We review here several NMR studies that have appeared during the past 5 or 6 years in the field of redox proteins of plants, yeasts and photosynthetic bacteria. These new results illustrate the recent biomolecular NMR evolution and provide new physiological models for understanding the different types of electron transfer, including glutaredoxins, thioredoxins and their dependent enzymes, the ferredoxin-NADP oxidoreductase complex, flavodoxins, the plastocyanin-cytochrome f complex, and cytochromes c.     

Pulmonary vasoreactivity in spontaneously hypertensive rats - Effects of endothelin-1 and leptin

Background

Systemic hypertension may be associated with an increased pulmonary vascular resistance, which we hypothesized could be, at least in part, mediated by increased leptin.

Methods

Vascular reactivity to phenylephrine (1 μmol/L), endothelin-1 (10 nmol/L) and leptin (0.001–100 nmol/L) was evaluated in endothelium-intact and -denuded isolated thoracic aorta and pulmonary arteries from spontaneously hypertensive versus control Wistar rats. Arteries were sampled for pathobiological evaluation and lung tissue for morphometric evaluation.

Results

In control rats, endothelin-1 induced a higher level of contraction in the pulmonary artery than in the aorta. After phenylephrine or endothelin-1 precontraction, leptin relaxed intact pulmonary artery and aortic rings, while no response was observed in denuded arteries. Spontaneously hypertensive rats presented with increased reactivity to phenylephrine and endothelin-1 in endothelium-intact pulmonary arteries. After endothelin-1 precontraction, endothelium-dependent relaxation to leptin was impaired in pulmonary arteries from hypertensive rats. In both strains of rats, aortic segments were more responsive to leptin than pulmonary artery. In hypertensive rats, pulmonary arteries exhibited increased pulmonary artery medial thickness, associated with increased expressions of preproendothelin-1, endothelin-1 receptors type A and B, inducible nitric oxide synthase and decreased endothelial nitric oxide synthase, together with decreased leptin receptor and increased suppressor of cytokine signaling 3 expressions.

Conclusions

Altered pulmonary vascular reactivity in hypertension may be related to a loss of endothelial buffering of vasoconstriction and decreased leptin-induced vasodilation in conditions of increased endothelin-1.     

Degradation of Activated K-Ras Orthologue via K-Ras-specific Lysine Residues Is Required for Cytokinesis

Mammalian cells encode three closely related Ras proteins, H-Ras, N-Ras, and K-Ras. Oncogenic K-Ras mutations frequently occur in human cancers, which lead to dysregulated cell proliferation and genomic instability. However, mechanistic role of the Ras isoform regulation have remained largely unknown. Furthermore, the dynamics and function of negative regulation of GTP-loaded K-Ras have not been fully investigated. Here, we demonstrate RasG, the Dictyostelium orthologue of K-Ras, is targeted for degradation by polyubiquitination. Both ubiquitination and degradation of RasG were strictly associated with RasG activity. High resolution tandem mass spectrometry (LC-MS/MS) analysis indicated that RasG ubiquitination occurs at C-terminal lysines equivalent to lysines found in human K-Ras but not in H-Ras and N-Ras homologues. Substitution of these lysine residues with arginines (4KR-RasG) diminished RasG ubiquitination and increased RasG protein stability. Cells expressing 4KR-RasG failed to undergo proper cytokinesis and resulted in multinucleated cells. Ectopically expressed human K-Ras undergoes polyubiquitin-mediated degradation in Dictyostelium, whereas human H-Ras and a Dictyostelium H-Ras homologue (RasC) are refractory to ubiquitination. Our results indicate the existence of GTP-loaded K-Ras orthologue-specific degradation system in Dictyostelium, and further identification of the responsible E3-ligase may provide a novel therapeutic approach against K-Ras-mutated cancers.     

Exserohilum israeli, a new species isolated from soil from Timna Park (Israel), and its physiological properties

Fungi isolated from soil in Timna Park (Israel) were found to belong to a new species of Exserohilum for which the name Exserohilum israeli sp. nov. is proposed. The main physiological properties of members of this species are discussed and the influence of temperature and copper concentrations on the growth and morphology of the fungus were investigated.     

Kinship and similarity in residency status structure female social networks in black‐and‐white colobus monkeys (colobus vellerosus)

Kinship shapes female social networks in many primate populations in which females remain in their natal group to breed. In contrast, it is unclear to which extent kinship affects the social networks in populations with female dispersal. Female Colobus vellerosus show routine facultative dispersal (i.e., some females remain philopatric and others disperse). This dispersal pattern allowed us to evaluate if facultative dispersed females form social networks shaped by an attraction to kin, to social partners with a high resource holding potential, or to similar social partners in terms of maturational stage, dominance rank, and residency status. During 2008 and 2009, we collected behavioral data via focal and ad libitum sampling of 61 females residing in eight groups at Boabeng‐Fiema, Ghana. We determined kinship based on partial pedigrees and genotypes at 17 short tandem repeat loci. Kinship influenced coalition and affiliation networks in three groups consisting of long‐term resident females with access to a relatively high number of female kin. In contrast, similar residency status was more important than kinship in structuring the affiliation network in one of two groups that contained recent female immigrants. In populations with female dispersal, the occurrence of kin structured social networks may not only depend on the kin composition of groups but also on how long the female kin have resided together. We found no consistent support for females biasing affiliation toward partners with high resource holding potential, possibly due to low levels of contest competition and small inter‐individual differences in resource holding potential. Am J Phys Anthropol 153:365–376, 2014. © 2013 Wiley Periodicals, Inc.     

Helix-length compensation studies reveal the adaptability of the VS ribozyme architecture

Compensatory mutations in RNA are generally regarded as those that maintain base pairing, and their identification forms the basis of phylogenetic predictions of RNA secondary structure. However, other types of compensatory mutations can provide higher-order structural and evolutionary information. Here, we present a helix-length compensation study for investigating structure-function relationships in RNA. The approach is demonstrated for stem-loop I and stem-loop V of the Neurospora VS ribozyme, which form a kissing-loop interaction important for substrate recognition. To rapidly characterize the substrate specificity (k(cat)/K(M)) of several substrate/ribozyme pairs, a procedure was established for simultaneous kinetic characterization of multiple substrates. Several active substrate/ribozyme pairs were identified, indicating the presence of limited substrate promiscuity for stem Ib variants and helix-length compensation between stems Ib and V. 3D models of the I/V interaction were generated that are compatible with the kinetic data. These models further illustrate the adaptability of the VS ribozyme architecture for substrate cleavage and provide global structural information on the I/V kissing-loop interaction. By exploring higher-order compensatory mutations in RNA our approach brings a deeper understanding of the adaptability of RNA structure, while opening new avenues for RNA research.