Possible Role of Horizontal Gene Transfer in the Colonization of Sea Ice by Algae

Diatoms and other algae not only survive, but thrive in sea ice. Among sea ice diatoms, all species examined so far produce ice-binding proteins (IBPs), whereas no such proteins are found in non-ice-associated diatoms, which strongly suggests that IBPs are essential for survival in ice. The restricted occurrence also raises the question of how the IBP genes were acquired. Proteins with similar sequences and ice-binding activities are produced by ice-associated bacteria, and so it has previously been speculated that the genes were acquired by horizontal transfer (HGT) from bacteria. Here we report several new IBP sequences from three types of ice algae, which together with previously determined sequences reveal a phylogeny that is completely incongruent with algal phylogeny, and that can be most easily explained by HGT. HGT is also supported by the finding that the closest matches to the algal IBP genes are all bacterial genes and that the algal IBP genes lack introns. We also describe a highly freeze-tolerant bacterium from the bottom layer of Antarctic sea ice that produces an IBP with 47% amino acid identity to a diatom IBP from the same layer, demonstrating at least an opportunity for gene transfer. Together, these results suggest that the success of diatoms and other algae in sea ice can be at least partly attributed to their acquisition of prokaryotic IBP genes

Confluence of resonant laser excitation and bi-directional quantum dot nuclear spin polarization

Resonant laser scattering along with photon correlation measurements have established the atom-like character of quantum dots. Here, we present measurements which challenge this identification for a wide range of experimental parameters: the absorption lineshapes that we measure at magnetic fields exceeding 1 Tesla indicate that the nuclear spins polarize by an amount that ensures locking of the quantum dot resonances to the incident laser frequency. In contrast to earlier experiments, this nuclear spin polarization is bi-directional, allowing the electron+nuclear spin system to track the changes in laser frequency dynamically on both sides of the quantum dot resonance. Our measurements reveal that the confluence of the laser excitation and nuclear spin polarization suppresses the fluctuations in the resonant absorption signal. A master equation analysis shows narrowing of the nuclear Overhauser field variance, pointing to potential applications in quantum information processing

Common Household Chemicals and the Allergy Risks in Pre-School Age Children

The risk of indoor exposure to volatile organic compounds (VOCs) on allergic airway diseases in children remains unknown.We examined the residential concentrations of VOCs, emitted from building materials, paints, furniture, and other lifestyle practices and the risks of multiple allergic diseases as well as the IgE-sensitization in pre-school age children in Sweden.In a case-control investigation (198 case children with asthma and allergy and 202 healthy controls), air samples were collected in the room where the child slept. The air samples were analyzed for the levels of eight classes of VOCs.A natural-log unit of summed propylene glycol and glycol ethers (PGEs) in bedroom air (equal to interquartile range, or 3.43 - 15.65 µg/m(3)) was associated with 1.5-fold greater likelihood of being a case (95% CI, 1.1 - 2.1), 1.5-fold greater likelihood of asthma (95% CI, 1.0 - 2.3), 2.8-fold greater likelihood of rhinitis (95% CI, 1.6 - 4.7), and 1.6-fold greater likelihood of eczema (95% CI, 1.1 - 2.3), accounting for gender, secondhand smoke, allergies in both parents, wet cleaning with chemical agents, construction period of the building, limonene, cat and dog allergens, butyl benzyl phthalate (BBzP), and di(2-ethylhexyl)phthalate (DEHP). When the analysis was restricted to the cases, the same unit concentration was associated with 1.8-fold greater likelihood of IgE-sensitization (95% CI, 1.1 - 2.8) compared to the non-IgE sensitized cases. No similar associations were found for the other classes of VOCs.We propose a novel hypothesis that PGEs in indoor air exacerbate and/or induce the multiple allergic symptoms, asthma, rhinitis and eczema, as well as IgE sensitization respectively

On the analysis of the contact angle for impacting droplets using a polynomial fitting approach

ractical considerations on the measurement of the dynamic contact angle and the spreading diameter of impacting droplets are discussed in this paper. The contact angle of a liquid is commonly obtained either by a polynomial or a linear fitting to the droplet profile around the triple phase point. Previous works have focused on quasi-static or sessile droplets, or in cases where inertia does not play a major role on the contact angle dynamics. Here, we study the effect of droplet shape, the order of the fitting polynomial, and the fitting domain, on the measurement of the contact angle on various stages following droplet impact where the contact line is moving. Our results, presented in terms of the optical resolution and the droplet size, show that a quadratic fitting provides the most consistent results for a range of various droplet shapes. As expected, our results show that contact angle values are less sensitive to the fitting conditions for the cases where the droplet can be approximated to a spherical cap. Our experimental conditions include impact events with liquid droplets of different sizes and viscosities on various substrates. In addition, validating past works, our results show that the maximum spreading diameter can be parameterised by the Weber number and the rapidly advancing contact angle

SpxA1 Involved in Hydrogen Peroxide Production, Stress Tolerance and Endocarditis Virulence in Streptococcus sanguinis

Streptococcus sanguinis is one of the most common agents of infective endocarditis. Spx proteins are a group of global regulators that negatively or positively control global transcription initiation. In this study, we characterized the spxA1 gene in S. sanguinis SK36. The spxA1 null mutant displayed opaque colony morphology, reduced hydrogen peroxide (H2O2) production, and reduced antagonistic activity against Streptococcus mutans UA159 relative to the wild type strain. The ΔspxA1 mutant also demonstrated decreased tolerance to high temperature, acidic and oxidative stresses. Further analysis revealed that ΔspxA1 also exhibited a ∼5-fold reduction in competitiveness in an animal model of endocarditis. Microarray studies indicated that expression of several oxidative stress genes was downregulated in the ΔspxA1 mutant. The expression of spxB and nox was significantly decreased in the ΔspxA1 mutant compared with the wild type. These results indicate that spxA1 plays a major role in H2O2 production, stress tolerance and endocarditis virulence in S. sanguinis SK36. The second spx gene, spxA2, was also found in S. sanguinis SK36. The spxA2 null mutant was found to be defective for growth under normal conditions and showed sensitivity to high temperature, acidic and oxidative stresses

The interaction of bacterial pathogens with platelets.

In recent years, the frequency of serious cardiovascular infections such as endocarditis has increased, particularly in association with nosocomially acquired antibiotic-resistant pathogens. Growing evidence suggests a crucial role for the interaction of bacteria with human platelets in the pathogenesis of cardiovascular infections. Here, we review the nature of the interactions between platelets and bacteria, and the role of these interactions in the pathogenesis of endocarditis and other cardiovascular diseases

Barley <i>SIX-ROWED SPIKE3</i> encodes a putative Jumonji C-type H3K9me2/me3 demethylase that represses lateral spikelet fertility

The VRS genes of barley control the fertility of the lateral spikelets on the barley inflorescence. Here, Bull et al. show that VRS3 encodes a putative Jumonji C-type histone demethylase that regulates expression of other VRS genes, and genes involved in stress, hormone and sugar metabolism

Adult-Age Inflammatory Pain Experience Enhances Long-Term Pain Vigilance in Rats

Background: Previous animal studies have illustrated a modulatory effect of neonatal pain experience on subsequent painrelated behaviors. However, the relationship between chronic pain status in adulthood and future pain perception remains unclear. Methodology/Principal Findings: In the current study, we investigated the effects of inflammatory pain experience on subsequent formalin-evoked pain behaviors and fear conditioning induced by noxious stimulation in adult rats. Our results demonstrated an increase of the second but not the first phase of formalin-induced pain behaviors in animals with a history of inflammatory pain that have recovered. Similarly, rats with persistent pain experience displayed facilitated acquisition and prolonged retention of pain-related conditioning. These effects of prior pain experience on subsequent behavior were prevented by repeated morphine administration at an early stage of inflammatory pain. Conclusions/Significance: These results suggest that chronic pain diseases, if not properly and promptly treated, may have a long-lasting impact on processing and perception of environmental threats. This may increase the susceptibility of patients to subsequent pain-related disorders, even when chronic pain develops in adulthood. These data highlight th

Human amnion epithelial cells rescue cell death via immunomodulation of microglia in a mouse model of perinatal brain injury

BACKGROUND: Human amnion epithelial cells (hAECs) are clonogenic and have been proposed to reduce inflammatory-induced tissue injury. Perturbation of the immune response is implicated in the pathogenesis of perinatal brain injury; modulating this response could thus be a novel therapy for treating or preventing such injury. The immunomodulatory properties of hAECs have been shown in other animal models, but a detailed investigation of the effects on brain immune cells following injury has not been undertaken. Here, we investigate the effects of hAECs on microglia, the first immune responders to injury within the brain. METHODS: We generated a mouse model combining neonatal inflammation and perinatal hyperoxia, both of which are risk factors associated with perinatal brain injury. On embryonic day 16 we administered lipopolysaccharide (LPS), or saline (control), intra-amniotically to C57Bl/6 J mouse pups. On postnatal day (P)0, LPS pups were placed in hyperoxia (65% oxygen) and control pups in normoxia for 14 days. Pups were given either hAECs or saline intravenously on P4. RESULTS: At P14, relative to controls, LPS and hyperoxia pups had reduced body weight, increased density of apoptotic cells (TUNEL) in the cortex, striatum and white matter, astrocytes (GFAP) in the white matter and activated microglia (CD68) in the cortex and striatum, but no change in total microglia density (Iba1). hAEC administration rescued the decreased body weight and reduced apoptosis and astrocyte areal coverage in the white matter, but increased the density of total and activated microglia. We then stimulated primary microglia (CD45(low)CD11b(+)) with LPS for 24 h, followed by co-culture with hAEC conditioned medium for 48 h. hAEC conditioned medium increased microglial phagocytic activity, decreased microglia apoptosis and decreased M1 activation markers (CD86). Stimulating hAECs for 24 h with LPS did not alter release of cytokines known to modulate microglia activity. CONCLUSIONS: These data demonstrate that hAECs can directly immunomodulate brain microglia, probably via release of trophic factors. This observation offers promise that hAECs may afford therapeutic utility in the management of perinatal brain injury

Central CD4+ T cell tolerance: deletion versus regulatory T cell differentiation

The diversion of MHC class II-restricted thymocytes into the regulatory T (Treg) cell lineage, similarly to clonal deletion, is driven by intrathymic encounter of agonist self-antigens. Somewhat paradoxically, it thus seems that the expression of an autoreactive T cell receptor is a shared characteristic of T cells that are subject to clonal deletion and those that are diverted into the Treg cell lineage. Here, we discuss how thymocyte-intrinsic and -extrinsic determinants may specify the choice between these two fundamentally different T cell fates