Exploring the UV spectral range to constrain the evolution of massive galaxies in varying environments and varying redshift

Las galaxias más masivas del Universo local son las galaxias de tipo temprano (del inglés, ETGs) que comprenden las galaxias elípticas y lenticulares. El grueso de sus poblaciones de estrellas son viejas y prácticamente no están formando nuevas estrellas. Su actividad de formación estelar no es lo que llegó a ser en las etapas tempranas del Universo, donde grandes cantidades de gas se transformaron en estrellas. La formación de estrellas se detuvo rápidamente y las ETGs evolucionaron como sistemas rojos y viejos. Cuáles fueron los mecanismos físicos responsables de detener la creación de nuevas estrellas sigue siendo un misterio, aunque se cree que las contribuciones de los núcleos activos de galaxias (del inglés, AGNs) pudieron transformar estos sistemas estelares en objetos evolucionando pasivamente con escasa formación estelar. Las estrellas viejas de las ETGs emiten la mayor parte de su luz en el rango espectral óptico. El óptico, sin embargo, es relativamente insensible a pequeñas fracciones de poblaciones estelares jóvenes, cuya luz domina en el rango ultravioleta (UV). Afortunadamente, el UV es un trazador óptimo de las poblaciones estelares más calientes como las estrellas jóvenes. Estudios fotométricos en el UV han puesto de manifiesto que las ETGs pueden tener formación de estrellas a un ritmo muy bajo. Sin embargo, el rango UV en los espectros de las ETGs no ha sido explorado para determinar sus poblaciones jóvenes. El objetivo de esta tesis es cuantificar estas poblaciones estelares jóvenes de las ETGs masivas usando las líneas de absorción de sus espectros. Hemos usado nuevos modelos de poblaciones estelares para analizar, por primera vez, índices espectrales ópticos y del UV cercano simultáneamente. Comparamos las observaciones con las predicciones de los modelos de dos parametrizaciones de las historias de formación estelar (del inglés, SFH) de las galaxias masivas. Primero hemos investigado si la formación de estrellas residual es una característica común entre la población de ETGs, mediante la suma de miles de espectros de galaxias masivas a un desplazamiento al rojo medio de z~0.4. De estos espectros sumados hemos podido obtener las fracciones de población joven en función de la masa de la galaxia. Hemos encontrado que las ETGs masivas tienen en promedio una fracción de estrellas jóvenes formadas en los últimos 2 mil millones de años por debajo del 1%, y que ésta fracción es mayor para las galaxias menos masivas. Esta tendencia con la masa es consistente con el hecho que las galaxias menos masivas tienen SFH más extendidas en el tiempo que las más masivas. También hemos visto que las galaxias masivas sintéticas de las simulaciones cosmológicas producen demasiadas estrellas de edades intermedias. Esto implica que los procesos para suprimir la formación de estrellas en galaxias masivas y mantenerla suprimida en el tiempo, aun necesitan ser comprendidos. Nuestros resultados ponen rigurosos límites que necesitan ser satisfechos por las simulaciones. Para intentar entender el origen de estas poblaciones jóvenes, hemos analizado espectros resueltos espacialmente para obtener información de dónde están situadas en las galaxias. Para ello, hemos analizado un tipo especial de ETGs: las galaxias más brillantes de los cúmulos de galaxias (del inglés, BCGs). Estas galaxias se encuentran en el centro de los potenciales gravitatorios de los cúmulos de galaxias. Nuestro estudio de 6 BCGs cercanas ha demostrado que sus estrellas jóvenes están en el interior de <2 kpc del centro de las galaxias, es decir, en los núcleos. Las pequeñas fracciones de estrellas jóvenes que encontramos son consistentes con un origen in-situ, es decir, la formación de estrellas residual puede producirse gracias al material reciclado de la muerte de estrellas de generaciones anteriores o del gas inicial residual. Sin embargo, debido a la ubicación de estos objetos, un origen ex-situ a través los efectos y procesos del entorno del no puede ser descartado. Estudiar las componentes estelares jóvenes en galaxias reliquias nos ayuda a entender los orígenes de la formación estelar reciente que detectamos en las galaxias ETGs normales. Estas galaxias reliquias, masivas y compactas, han sobrevivido intactas desde su formación a alto desplazamiento al rojo hasta el Universo local, es decir, sin haber experimentado un crecimiento tanto en tamaño como en masa a través de fusiones e interacciones con otras galaxias. Por ello, hemos estudiado la contribución de las poblaciones jóvenes en la región central de 1 kpc de la galaxia NGC 1277, la galaxia reliquia por excelencia del Universo cercano. Encontramos una población joven que contribuye menos del 1%, similar a los resultados previos, lo que apunta a que la formación estelar reciente encontrada en galaxias masivas ETGs puede estar relacionada con los procesos intrínsecos de las galaxias.Early-type galaxies (ETGs), consisting of ellipticals and lenticulars, are the most massive galaxies in the local Universe. The bulk of their stellar populations are characterised as being old with negligible recent star formation activity, having followed a passive evolution from the high-redshift Universe to the present day. Their star formation activity is not what used to be at the early Universe (z > 2), where large amounts of gas were transformed into stars. Star formation was virtually extinguished in rather short time and ETGs evolved as red and dead objects. The exact physical mechanisms responsible for quenching the star formation in these massive systems at high-redshift is not completely resolved. Although, it is widely considered that AGN feedback could turn these stellar systems into passively evolving objects without significant formation of new stars. There is growing observational and theoretical evidences for a two-phase formation scenario for ETGs. According to this picture, during the first phase the cores of present-day ETGs are formed at z > 2 dissipatively, while in the second phase the outer regions are a result of mergers and accretion. This is supported by a large number of studies that have shown that massive galaxies at z > 2 are more compact than their local counterparts, and have experienced significant growth both in size and, to a lesser degree, in mass. This suggests that these high-z massive compacts are the cores of local ETGs formed at high redshift, while the outer regions are where the accreted material due to dissipationless mergers (i.e. gas-poor) is deposited. This second phase is mostly ”dry”, i.e. does not trigger star formation, at least not in any efficient way. The bulk of the stars in ETGs are ancient and emit much of their light in the optical spectral range. However, the optical is relatively insensitive to small fractions of young stellar populations, whose light dominate the ultraviolet (UV). Studies of the optical range are therefore, biased to the old stellar populations. Fortunately, the UV is an optimal tracer of the hottest stellar populations such as young stars. Photometric studies in the UV have previously suggested that ETGs might have recent low-level star formation. However, the UV window of ETG’s spectra has not been explored for determining the youngest stellar populations. This thesis aims to quantify these young stellar populations by using spectral absorption features of massive ETGs. We exploit state-of-the-art stellar population models based on empirical stellar libraries to analyse, for the first time, observed optical and near-UV line-strength indices simultaneously. We compare observations with model predictions from two assumed simple parameterisations of the star formation history (SFH) of massive galaxies. We first explore if the residual star formation is ubiquitous among the massive ETG population by stacking thousands of galaxy spectra at redshift of z ∼ 0.4. We derive mass fractions of the young stellar component as a function of mass. We find that massive galaxies show, on average, a sub-one percent fraction of young stars formed within the last 2 Gyr, and that this fraction is larger for less massive galaxies. This trend with mass is consistent with the fact that less massive galaxies have more extended SFHs than their more massive counterparts and also may be related to the fact that AGN feedback stops the formation of new stars more efficiently for more massive galaxies. We also find that synthetic massive galaxies from cosmological numerical simulations significantly overproduce both intermediate and young stellar populations. This means that the recipe to quench the star formation in these galaxies, and perhaps to maintain them quenched, still needs to be fully understood. However, the results obtained here put stringent constrains that must be satisfied by these simulations. In order to understand the origin of these young stars, we turned to spatially resolved spectroscopy to tell us precisely where they are located. For this purpose, we analyse a special type of ETGs: the brightest cluster galaxies (BCGs). These galaxies are located in the centres of the gravitational potential wells of galaxy clusters. Our study of 6 nearby BCGs indicate that their young stars are located within < 2 kpc of the galaxy centres, i.e. in their cores. Our findings of small young mass fractions are consistent with being formed in-situ, likely residual star formation from recycled material of dying stars from previous generations. However, due to the particular location of these massive systems, an ex-situ origin through environmental processes can not be ruled out. The study of young stellar components in so-called ”relic galaxies” offers us unique clues to understand the possible origins of the recent star formation that we detect in normal ETGs. These massive compact relic galaxies are thought to have survived untouched since their formation at high-z until the presentday, i.e. without having gone through a second phase that is characterised by a growth in size and mass by accretion. For this purpose, we studied the young stellar contribution in the 1 kpc central region of NGC 1277, a well studied galaxy that is regarded as the prototypical relic galaxy in the nearby Universe. We find a sub-one percent level of young mass fractions, similar to our samples of massive ETGs, which points to intrinsic, in-situ, processes that trigger the formation of these young stars

Novel Molecular Methods for Discovery and Engineering of Biocatalysts From Uncultured Marine Microorganisms

Metagenomics is a powerful cultivation-independent approach, which can be applied to gain access to the biocatalysts from uncultured marine microorganisms. Discovery of marine biocatalysts by this approach, in general, involves four main steps. First, a metagenomic library containing a pool of biocatalyst-encoding genes is constructed from a marine environment, which can be done by various methods, including cloning of enzymatically-digested DNA, uncut DNA, and PCR-amplified products. Second, the metagenomic library is screened for the genes of interest by employing the activity assay of expression product, in situ hybridization, or Polymerase Chain Reaction (PCR). Third, the obtained target genes, both functional and phylogenetic genes, are sequenced and analysed by using bioinformatic tools in order to gain information on the functional and structural properties as well as the microbial sources of the encoded biocatalysts. Finally, the target genes are expressed in suitable microbial hosts, thereby producing the corresponding recombinant biocatalysts. All existing methods in engineering of marine biocatalysts for the performance improvement can be classified into two main strategies: (i) rational design and (ii) directed evolution. Rational design, which may include the use of resctriction enzyme(s) and splicing by overlap extension (SOE), requires information on the biocatalyst`s structural and functional properties to alter specific amino acid(s). Whereas directed evolution, including error-prone PCR technique and gene shuffling, needs no such information

Immobilisation of electrochemically active bacteria on screen-printed electrodes for rapid in situ toxicity biosensing

Microbial biosensors can be an excellent alternative to classical methods for toxicity monitoring, which are time-consuming and not sensitive enough. However, bacteria typically connect to electrodes through biofllm formation, leading to problems due to lack of uniformity or long device production times. A suitable immobilisation technique can overcome these challenges. Still, they may respond more slowly than biofllm-based electrodes because bacteria gradually adapt to electron transfer during biofllm formation. In this study, we propose a controlled and reproducible way to fabricate bacteria-modified electrodes. The method consists of an immobilisation step using a cellulose matrix, followed by an electrode polarization in the presence of ferricyanide and glucose. Our process is short, reproducible and led us to obtain ready-to-use electrodes featuring a high-current response. An excellent shelf-life of the immobilised electrochemically active bacteria was demonstrated for up to one year. After an initial 50% activity loss in the first month, no further declines have been observed over the following 11 months. We implemented our bacteria-modified electrodes to fabricate a lateral flow platform for toxicity monitoring using formaldehyde (3%). Its addition led to a 59% current decrease approximately 20 min after the toxic input. The methods presented here offer the ability to develop a high sensitivity, easy to produce, and long shelf life bacteria-based toxicity detectors. (C) 2020 The Author(s). Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences, Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences

An unusual flavin-dependent halogenase from the metagenome of the marine sponge Theonella swinhoei WA

The authors thank EU BlueGenics (Seventh Framework Programme, Collaborative project “BlueGenics”, Grant no. 311848 RJMG and JP), the SNF (Grant no.205321_165695 to JP), the Helmut Horten Foundation (JP), and ERAIB (Grant no. 031A338A KHVP and RJMG) for funding.Uncultured bacteria from sponges have been demonstrated to be responsible for the generation of many potent, bioactive natural products including halogenated metabolites.1 The identification of gene clusters from the metagenomes of such bacterial communities enables the discovery of enzymes that mediate new and useful chemistries and allows insight to be gained into the biogenesis of potentially pharmacologically important natural products. Here we report a new pathway to the keramamides (krm); the first functional evidence for the existence of a distinct producer in the Theonella swinhoei WA chemotype is revealed, and a key enzyme on the pathway, a unique flavin dependent halogenase with a broad substrate specificity, and with potential as a useful new biocatalytic tool is described.PostprintPeer reviewe

Delamination technique together with longitudinal incisions for treatment of Chiari I/syringomyelia complex: a prospective clinical study

<p>Abstract</p> <p>Background</p> <p>Treatment modalities in Chiari malformation type 1(CMI) accompanied by syringomyelia have not yet been standardized. Pathologies such as a small posterior fossa and thickened dura mater have been discussed previously. Various techniques have been explored to enlarge the foramen magnum and to expand the dura. The aim of this clinical study was to explore a new technique of excision of the external dura accompanied by widening the cisterna magna and making longitudinal incisions in the internal dura, without disturbing the arachnoid.</p> <p>Methods</p> <p>Ten patients with CMI and syringomyelia, operated between 2004 and 2006, formed this prospective series. All cases underwent foramen magnum decompression of 3 × 3 cm area with C1–C2 (partial) laminectomy, resection of foramen magnum fibrous band, excision of external dura, delamination and widening of internal dura with longitudinal incisions.</p> <p>Results</p> <p>Patients were aged between 25 and 58 years and occipital headache was the most common complaint. The mean duration of preoperative symptoms was 4 years and the follow-up time was 25 months. Clinical progression was halted for all patients; eight patients completely recovered and two reported no change. In one patient, there was a transient cerebrospinal fluid (CSF) fistula that was treated with tissue adhesive. While syringomyelia persisted radiologically with radiological stability in five patients; for three patients the syringomyelic cavity decreased in size, and for the remaining two it regressed completely.</p> <p>Conclusion</p> <p>Removal of the fibrous band and the outer dural layer, at level of foramen magnum, together with the incision of inner dural layer appears to be good technique in adult CMI patients. The advantages are short operation time, no need for duraplasty, sufficient posterior fossa decompression, absence of CSF fistulas as a result of extra arachnoidal surgery, and short duration of hospitalization. Hence this surgical technique has advantages compared to other techniques.</p

Isolation of non-tuberculous mycobacteria from pastoral ecosystems of Uganda: Public Health significance

<p>Abstract</p> <p>Background</p> <p>The importance of non-tuberculous mycobacteria (NTM) infections in humans and animals in sub-Saharan Africa at the human-environment-livestock-wildlife interface has recently received increased attention. NTM are environmental opportunistic pathogens of humans and animals. Recent studies in pastoral ecosystems of Uganda detected NTM in humans with cervical lymphadenitis and cattle with lesions compatible with bovine tuberculosis. However, little is known about the source of these mycobacteria in Uganda. The aim of this study was to isolate and identify NTM in the environment of pastoral communities in Uganda, as well as assess the potential risk factors and the public health significance of NTM in these ecosystems.</p> <p>Method</p> <p>A total of 310 samples (soil, water and faecal from cattle and pigs) were examined for mycobacteria. Isolates were identified by the INNO-Lipa test and by 16S rDNA sequencing. Additionally, a questionnaire survey involving 231 pastoralists was conducted during sample collection. Data were analysed using descriptive statistics followed by a multivariable logistic regression analysis.</p> <p>Results</p> <p>Forty-eight isolates of NTM were detected; 25.3% of soil samples, 11.8% of water and 9.1% from animal faecal samples contained mycobacteria. Soils around water sources were the most contaminated with NTM (29.8%). Of these samples, <it>M. fortuitum-peregrinum </it>complex, <it>M. avium </it>complex, <it>M. gordonae</it>, and <it>M. nonchromogenicum </it>were the most frequently detected mycobacteria. Drinking untreated compared to treated water (OR = 33), use of valley dam versus stream water for drinking and other domestic use (OR = 20), sharing of water sources with wild primates compared to antelopes (OR = 4.6), sharing of water sources with domestic animals (OR = 5.3), and close contact with cattle or other domestic animals (OR = 13.8) were the most plausible risk factors for humans to come in contact with NTM in the environment.</p> <p>Conclusions</p> <p>The study detected a wide range of potentially pathogenic NTM from the environment around the pastoral communities in Uganda. Drinking untreated water and living in close contact with cattle or other domestic animals may be risk factors associated with the possibility of humans and animals acquiring NTM infections from these ecosystems.</p

Predictors of HBeAg status and hepatitis B viraemia in HIV-infected patients with chronic hepatitis B in the HAART era in Brazil

<p>Abstract</p> <p>Background</p> <p>HBV-HIV co-infection is associated with an increased liver-related morbidity and mortality. However, little is known about the natural history of chronic hepatitis B in HIV-infected individuals under highly active antiretroviral therapy (HAART) receiving at least one of the two drugs that also affect HBV (TDF and LAM). Information about HBeAg status and HBV viremia in HIV/HBV co-infected patients is scarce. The objective of this study was to search for clinical and virological variables associated with HBeAg status and HBV viremia in patients of an HIV/HBV co-infected cohort.</p> <p>Methods</p> <p>A retrospective cross-sectional study was performed, of HBsAg-positive HIV-infected patients in treatment between 1994 and 2007 in two AIDS outpatient clinics located in the São Paulo metropolitan area, Brazil. The baseline data were age, sex, CD4 T+ cell count, ALT level, HIV and HBV viral load, HBV genotype, and duration of antiretroviral use. The variables associated to HBeAg status and HBV viremia were assessed using logistic regression.</p> <p>Results</p> <p>A total of 86 HBsAg patients were included in the study. Of these, 48 (56%) were using combination therapy that included lamivudine (LAM) and tenofovir (TDF), 31 (36%) were using LAM monotherapy, and 7 patients had no previous use of either one. Duration of use of TDF and LAM varied from 4 to 21 and 7 to 144 months, respectively. A total of 42 (48. 9%) patients were HBeAg positive and 44 (51. 1%) were HBeAg negative. The multivariate analysis revealed that the use of TDF for longer than 12 months was associated with undetectable HBV DNA viral load (serum HBV DNA level < 60 UI/ml) (<it>p </it>= 0. 047). HBeAg positivity was associated with HBV DNA > 60 UI/ml (p = 0. 001) and ALT levels above normality (<it>p </it>= 0. 038).</p> <p>Conclusion</p> <p>Prolonged use of TDF containing HAART is associated with undetectable HBV DNA viral load. HBeAg positivity is associated with HBV viremia and increased ALT levels.</p