Host-specific symbiotic requirement of BdeAB, a RegR-controlled RND-type efflux system in Bradyrhizobium japonicum

Multidrug efflux systems not only cause resistance against antibiotics and toxic compounds but also mediate successful host colonization by certain plant-associated bacteria. The genome of the nitrogen-fixing soybean symbiont Bradyrhizobium japonicum encodes 24 members of the family of resistance/nodulation/cell division (RND) multidrug efflux systems, of which BdeAB is genetically controlled by the RegSR two-component regulatory system. Phylogenetic analysis of the membrane components of these 24 RND-type transporters revealed that BdeB is more closely related to functionally characterized orthologs in other bacteria, including those associated with plants, than to any of the other 23 paralogs in B. japonicum. A mutant with a deletion of the bdeAB genes was more susceptible to inhibition by the aminoglycosides kanamycin and gentamicin than the wild type, and had a strongly decreased symbiotic nitrogen-fixation activity on soybean, but not on the alternative host plants mungbean and cowpea, and only very marginally on siratro. The host-specific role of a multidrug efflux pump is a novel feature in the rhizobia-legume symbioses. Consistent with the RegSR dependency of bdeAB, a B. japonicum regR mutant was found to have a greater sensitivity against the two tested antibiotics and a symbiotic defect that is most pronounced for soybea

Biomonitoring of Indoor Air Fungal or Chemical Toxins with Caenorhabditis elegans nematodes

Bad indoor air quality due to toxins and other impurities can have a negative impact on human well-being, working capacity and health. Therefore, reliable methods to monitor the health risks associated with exposure to hazardous indoor air agents are needed. Here, we have used transgenic Caenorhabditis elegans nematode strains carrying stress-responsive fluorescent reporters and evaluated their ability to sense fungal or chemical toxins, especially those that are present in moisture-damaged buildings. Liquid-based or airborne exposure of nematodes to mycotoxins, chemical agents or damaged building materials reproducibly resulted in time- and dose-dependent fluorescent responses, which could be quantitated by either microscopy or spectrometry. Thus, the C. elegans nematodes present an easy, ethically acceptable and comprehensive in vivo model system to monitor the response of multicellular organisms to indoor air toxicity.Peer reviewe

The nitric oxide response in plant-associated endosymbiotic bacteria

Nitric oxide (NO) is a gaseous signalling molecule which becomes very toxic due to its ability to react with multiple cellular targets in biological systems. Bacterial cells protect against NO through the expression of enzymes that detoxify this molecule by oxidizing it to nitrate or reducing it to nitrous oxide or ammonia. These enzymes are haemoglobins, c-type nitric oxide reductase, flavorubredoxins and the cytochrome c respiratory nitrite reductase. Expression of the genes encoding these enzymes is controlled by NO-sensitive regulatory proteins. The production of NO in rhizobia–legume symbiosis has been demonstrated recently. In functioning nodules, NO acts as a potent inhibitor of nitrogenase enzymes. These observations have led to the question of how rhizobia overcome the toxicity of NO. Several studies on the NO response have been undertaken in two non-dentrifying rhizobial species, Sinorhizobium meliloti and Rhizobium etli, and in a denitrifying species, Bradyrhizobium japonicum. In the present mini-review, current knowledge of the NO response in those legume-associated endosymbiotic bacteria is summarized

Increased tooth brushing frequency is associated with reduced gingival pocket bacterial diversity in patients with intracranial aneurysms

Objectives The objective of this study was to investigate the association of tooth brushing frequency and bacterial communities of gingival crevicular fluid in patients subjected to preoperative dental examination prior to operative treatment for unruptured intracranial aneurysms. Methods Gingival crevicular fluid samples were taken from their deepest gingival pocket from a series of hospitalized neurosurgical patients undergoing preoperative dental screening (n = 60). The patients were asked whether they brushed their teeth two times a day, once a day, or less than every day. Total bacterial DNA was isolated and the V3–V4 region of the 16S rRNA gene was amplificated. Sequencing was performed with Illumina’s 16S metagenomic sequencing library preparation protocol and data were analyzed with QIIME (1.9.1) and R statistical software (3.3.2). Results Bacterial diversity (Chao1 index) in the crevicular fluid reduced along with reported tooth brushing frequency (p = 0.0002; R2 = 34%; p (adjusted with age and sex) = 0.09; R2 = 11%) showing that patients who reported brushing their teeth twice a day had the lowest bacterial diversity. According to the differential abundant analysis between the tooth brushing groups, tooth brushing associated with two phyla of fusobacteria [p = 0.0001; p = 0.0007], and one bacteroidetes (p = 0.004) by reducing their amounts. Conclusions Tooth brushing may reduce the gingival bacterial diversity and the abundance of periodontal bacteria maintaining oral health and preventing periodontitis, and thus it is highly recommended for neurosurgical patients

Patterns in airborne pollen and other primary biological aerosol particles (PBAP), and their contribution to aerosol mass and number in a boreal forest

We studied variation in concentrations of airborne pollen and other particles of biological origin in a boreal forest in Finland during 2003–2004. The highest concentrations of pollen were observed in late spring and early summer, whereas the peak concentrations of other particles of biological origin (including e.g. fungal spores) occurred in August–September. Although the patterns in concentrations in 2003 and 2004 were similar, the concentration levels were significantly different between the years. The contribution of pollen and other particles of biological origin led to an increase in the measured particulate matter (PM) mass during the pollen season (mass of pollen and other particles of biological origin 5.9 and 0.4 μg m–3, respectively, in respect to PMtotal mass of 9.9 μg m–3) but the effect on total particle number was negligible. The other particles of biological origin constituted the largest fraction of measured primary biological aerosol particle (PBAP) numbers (~99%), whereas pollen showed a higher relative mass fraction (~97%) of PBAP. These results underline the important contribution of PBAP to coarse atmospheric particle mass providing up to 65% of the total mass during the peak pollen season

Social and cultural origins of motivations to volunteer a comparison of university students in six countries

Although participation in volunteering and motivations to volunteer (MTV) have received substantial attention on the national level, particularly in the US, few studies have compared and explained these issues across cultural and political contexts. This study compares how two theoretical perspectives, social origins theory and signalling theory, explain variations in MTV across different countries. The study analyses responses from a sample of 5794 students from six countries representing distinct institutional contexts. The findings provide strong support for signalling theory but less so for social origins theory. The article concludes that volunteering is a personal decision and thus is influenced more at the individual level but is also impacted to some degree by macro-level societal forces

Time-Gated Raman Spectroscopy for Quantitative Determination of Solid-State Forms of Fluorescent Pharmaceuticals

Raman spectroscopy is widely used for quantitative pharmaceutical analysis, but a common obstacle to its use is sample fluorescence masking the Raman signal. Time-gating provides an instrument-based method for rejecting fluorescence through temporal resolution of the spectral signal and allows Raman spectra of fluorescent materials to be obtained. An additional practical advantage is that analysis is possible in ambient lighting. This study assesses the efficacy of time-gated Raman spectroscopy for the quantitative measurement of fluorescent pharmaceuticals. Time-gated Raman spectroscopy with a 128 X (2) X 4 CMOS SPAD detector was applied for quantitative analysis of ternary mixtures of solid-state forms of the model drug, piroxicam (PRX). Partial least-squares (PLS) regression allowed quantification, with Raman-active time domain selection (based on visual inspection) improving performance. Model performance was further improved by using kernel-based regularized least-squares (RLS) regression with greedy feature selection in which the data use in both the Raman shift and time dimensions was statistically optimized. Overall, time-gated Raman spectroscopy, especially with optimized data analysis in both the spectral and time dimensions, shows potential for sensitive and relatively routine quantitative analysis of photoluminescent pharmaceuticals during drug development and manufacturing

Comparison of the optical light curves of hydrogen-rich and hydrogen-poor type II supernovae

Type II supernovae (SNe II) show strong hydrogen features in their spectra throughout their whole evolution, while type IIb supernovae (SNe IIb) spectra evolve from dominant hydrogen lines at early times to increasingly strong helium features later on. However, it is currently unclear whether the progenitors of these SN types form a continuum in pre-SN hydrogen mass or whether they are physically distinct. SN light-curve morphology directly relates to progenitor and explosion properties such as the amount of hydrogen in the envelope, the pre-SN radius, the explosion energy, and the synthesized mass of radioactive material. In this work, we study the morphology of the optical-wavelength light curves of hydrogen-rich SNe II and hydrogen-poor SNe IIb to test whether an observational continuum exists between the two. Using a sample of 95 SNe (73 SNe II and 22 SNe IIb), we define a range of key observational parameters and present a comparative analysis between both types. We find a lack of events that bridge the observed properties of SNe II and IIb. Light-curve parameters such as rise times and post-maximum decline rates and curvatures clearly separate both SN types and we therefore conclude that there is no continuum, with the two SN types forming two observationally distinct families. In the V band a rise time of 17 d (SNe II lower and SNe IIb higher), and a magnitude difference between 30 and 40 d post-explosion of 0.4 mag (SNe II lower and SNe IIb higher) serve as approximate thresholds to differentiate both types.Fil: Pessi, Priscila Jael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Folatelli, Gaston. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Anderson, J. P.. European Southern Observatory Chile.; ChileFil: Bersten, Melina Cecilia. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Burns, C.. Observatories Of The Carnegie Institution For Science; Estados UnidosFil: Contreras, C.. Las Campanas Observatory; Chile. Space Telescope Science Institute; Estados UnidosFil: Davis, S.. Florida State University; Estados UnidosFil: Englert Urrutia, Brenda Nahir. Ministerio de Ciencia. Tecnología e Innovación Productiva. Agencia Nacional de Promoción Científica y Tecnológica; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Hamuy, M.. Universidad de Chile; ChileFil: Hsiao, Eric. Florida State University; Estados UnidosFil: Martinez, Laureano. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Morrell, Nidia Irene. Las Campanas Observatory; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Phillips, M. M.. Las Campanas Observatory; ChileFil: Suntzeff, N.. Texas A&M University; Estados UnidosFil: Stritzinger, M. D.. University Aarhus; Dinamarc

Type II supernovae from the Carnegie Supernova Project-I. II. Physical parameter distributions from hydrodynamical modelling

Linking supernovae to their progenitors is a powerful method for furthering our understanding of the physical origin of their observed differences, while at the same time testing stellar evolution theory. In this second study of a series of three papers where we characterise SNe II to understand their diversity, we derive progenitor properties (initial and ejecta masses, and radius), explosion energy, $^{56}$Ni mass, and its degree of mixing within the ejecta for a large sample of SNe II. This dataset was obtained by the Carnegie Supernova Project-I and is characterised by a high cadence of their optical and NIR light curves and optical spectra that were homogeneously observed and processed. A large grid of hydrodynamical models and a fitting procedure based on MCMC methods were used to fit the bolometric light curve and the evolution of the photospheric velocity of 53 SNe II. We infer ejecta masses between 7.9 and 14.8 $M_{\odot}$, explosion energies between 0.15 and 1.40 foe, and $^{56}$Ni masses between 0.006 and 0.069 $M_{\odot}$. We define a subset of 24~SNe (the `gold sample') with well-sampled bolometric light curves and expansion velocities for which we consider the results more robust. Most SNe~II in the gold sample ($\sim$88%) are found with ejecta masses in the range of $\sim$8-10 $M_{\odot}$, coming from low zero-age main-sequence masses (9-12 $M_{\odot}$). The modelling of the initial-mass distribution of the gold sample gives an upper mass limit of 21.3$^{+3.8}_{-0.4}$ $M_{\odot}$ and a much steeper distribution than that for a Salpeter massive-star IMF. This IMF incompatibility is due to the large number of low-mass progenitors found -- when assuming standard stellar evolution. This may imply that high-mass progenitors lose more mass during their lives than predicted. However, a deeper analysis of all stellar evolution assumptions is required to test this hypothesis.Comment: Accepted for publication in Astronomy & Astrophysic