170 research outputs found
Characterization of As(III) oxidizing Achromobacter sp. strain N2 : effects on arsenic toxicity and translocation in rice
Achromobacter sp. strain N2 was isolated from a pyrite-cinder-contaminated soil and presented plant growth promoting traits (ACC deaminase activity, production of indole-3-acetic and jasmonic acids, siderophores secretion, and phosphate solubilization) and arsenic transformation abilities. Achromobacter sp. strain N2 was resistant to different metals and metalloids, including arsenate (100 mM) and arsenite (5 mM). The strain was resistant to ionic stressors (i.e., arsenate and NaCl), whereas bacterial growth was impaired by osmotic stress. Strain N2 was able to oxidize 1.0 mmol L-1 of arsenite to arsenate in 72 h. This evidence was supported by the retrieval of an arsenite oxidase AioA gene highly homologous to arsenite oxidases of Achromobacter and Alcaligenes species. Rice seeds of Oryza sativa (var. Loto) were bio-primed with ACCD-induced and non-induced cells in order to evaluate the effect of inoculation on rice seedlings growth and arsenic uptake. The bacterization with ACCD-induced cells significantly improved seed germination and seedling heights if compared with the seeds inoculated with non-induced cells and non-primed seeds. Enhanced arsenic uptake was evidenced in the presence of ACCD-induced cells, suggesting a role of ACCD activity on the mitigation of the toxicity of arsenic accumulated by the plant. This kind of responses should be taken into account when proposing PGP strains for improving plant growth in arsenic-rich soils
Phylogenetic Structure and Metabolic Properties of Microbial Communities in Arsenic-Rich Waters of Geothermal Origin
Arsenic (As) is a toxic element released in aquatic environments by geogenic processes
or anthropic activities. To counteract its toxicity, several microorganisms have developed
mechanisms to tolerate and utilize it for respiratory metabolism. However, still little is
known about identity and physiological properties of microorganisms exposed to natural
high levels of As and the role they play in As transformation and mobilization processes.
This work aims to explore the phylogenetic composition and functional properties of
aquatic microbial communities in As-rich freshwater environments of geothermal origin
and to elucidate the key microbial functional groups that directly or indirectly may
influence As-transformations across a natural range of geogenic arsenic contamination.
Distinct bacterial communities in terms of composition and metabolisms were found.
Members of Proteobacteria, affiliated to Alpha- and Betaproteobacteria were mainly
retrieved in groundwaters and surface waters, whereas Gammaproteobacteria were
the main component in thermal waters. Most of the OTUs from thermal waters were
only distantly related to 16S rRNA gene sequences of known taxa, indicating the
occurrence of bacterial biodiversity so far unexplored. Nitrate and sulfate reduction and
heterotrophic As(III)-oxidization were found as main metabolic traits of the microbial
cultivable fraction in such environments. No growth of autotrophic As(III)-oxidizers,
autotrophic and heterotrophic As(V)-reducers, Fe-reducers and oxidizers, Mn-reducers
and sulfide oxidizers was observed. The ars genes, involved in As(V) detoxifying
reduction, were found in all samples whereas aioA [As(III) oxidase] and arrA genes
[As(V) respiratory reductase] were not found. Overall, we found that As detoxification
processes prevailed over As metabolic processes, concomitantly with the intriguing
occurrence of novel thermophiles able to tolerate high levels of As
Gas Pixel Detectors for X-ray Polarimetry applications
We discuss a new class of Micro Pattern Gas Detectors, the Gas Pixel Detector
(GPD), in which a complete integration between the gas amplification structure
and the read-out electronics has been reached. An Application-Specific
Integrated Circuit (ASIC) built in deep sub-micron technology has been
developed to realize a monolithic device that is, at the same time, the
pixelized charge collecting electrode and the amplifying, shaping and charge
measuring front-end electronics. The CMOS chip has the top metal layer
patterned in a matrix of 80 micron pitch hexagonal pixels, each of them
directly connected to the underneath electronics chain which has been realized
in the remaining five layers of the 0.35 micron VLSI technology. Results from
tests of a first prototype of such detector with 2k pixels and a full scale
version with 22k pixels are presented. The application of this device for
Astronomical X-Ray Polarimetry is discussed. The experimental detector response
to polarized and unpolarized X-ray radiation is shown. Results from a full
MonteCarlo simulation for two astronomical sources, the Crab Nebula and the
Hercules X1, are also reported.Comment: 16 pages, 20 figures, accepted for publication in Nuclear Instruments
and Methods in Physics Research Section
Opening a New Window to Fundamental Physics and Astrophysics: X-ray Polarimetry
An extensive theoretical literature predicts that X-ray Polarimetry can
directly determine relevant physical and geometrical parameters of
astrophysical sources, and discriminate between models further than allowed by
spectral and timing data only. X-ray Polarimetry can also provide tests of
Fundamental Physics. A high sensitivity polarimeter in the focal plane of a New
Generation X-ray telescope could open this new window in the High Energy Sky.Comment: 8 pages 1 table 14 figure
Degradation of a benzene–toluene mixture by hydrocarbon-adapted bacterial communities
We examined the rate of degradation of a benzene–toluene mixture in aerobic microcosms prepared with samples of an aquifer that lies below a petrochemical plant (SIReN, UK). Five samples exposed to different concentrations of benzene (from 0.6 to 317 mg l−1) were used. Fast degradation (approx. 1–6 mg l−1 day−1) of both contaminants was observed in all groundwater samples and complete degradation was recorded by the seventh day except for one sample. We also identified the microbial community in each of the samples by culture-independent techniques. Two of the less impacted samples harbour the aerobic benzene degrader Pseudomonas fluorescens, while Acidovorax and Arthrobacter spp. were found in the most polluted sample and are consistent with the population observed in situ. Hydrogenophaga was found in the deepest sample while Rhodoferax spp. were recovered in an alkaline sample (pH 8.4) and may also be implicated in benzene degradation. Time series analysis shows that each of the samples has a different community but they remain stable over the degradation period. This study provides new information on a well not previously studied (no. 309s) and confirms that adapted communities have the ability to degrade hydrocarbon mixtures and could be used in further bioaugmentation approaches in contaminated sites
A Recent Class of Chemosensory Neurons Developed in Mouse and Rat
In most animal species, the vomeronasal organ ensures the individual recognition of conspecifics, a prerequisite for a successful reproduction. The vomeronasal organ expresses several receptors for pheromone detection. Mouse vomeronasal type-2 receptors (V2Rs) are restricted to the basal neurons of this organ and organized in four families. Family-A, B and D (family ABD) V2Rs are expressed monogenically (one receptor per neuron) and coexpress with either Vmn2r1 or Vmn2r2, two members of family-C V2Rs. Thus, basal neurons are characterized by specific combinations of two V2Rs. To investigate this issue, we raised antibodies against all family-C V2Rs and analyzed their expression pattern. We found that six out of seven family-C V2Rs (Vmn2r2-7) largely coexpressed and that none of the anti-Vmn2r2-7 antibodies significantly stained Vmn2r1 positive neurons. Thus, basal neurons are divided into two complementary subsets. The first subset (Vmn2r1-positive) preferentially coexpresses a distinct group of family-ABD V2Rs, whereas the second subset (Vmn2r2-7-positive) coexpresses the remaining group of V2Rs. Phylogenetic reconstruction and the analysis of genetic loci in various species reveal that receptors expressed by this second neuronal subset are recent branches of the V2R tree exclusively present in mouse and rat. Conversely, V2Rs expressed in Vmn2r1 positive neurons, are phylogenetically ancient and found in most vertebrates including rodents. Noticeably, the more recent neuronal subset expresses a type of Major Histocompatibility Complex genes only found in murine species. These results indicate that the expansion of the V2R repertoire in a murine ancestor occurred with the establishment of a new population of vomeronasal neurons in which coexists the polygenic expression of a recent group of family-C V2Rs (Vmn2r2-7) and the monogenic expression of a recent group of family-ABD V2Rs. This evolutionary innovation could provide a molecular rationale for the exquisite ability in individual recognition and mate choice of murine species
A new class of glycomimetic drugs to prevent free fatty acid-induced endothelial dysfunction
Background: Carbohydrates play a major role in cell signaling in many biological processes. We have developed a set of glycomimetic drugs that mimic the structure of carbohydrates and represent a novel source of therapeutics for endothelial dysfunction, a key initiating factor in cardiovascular complications. Purpose: Our objective was to determine the protective effects of small molecule glycomimetics against free fatty acidinduced endothelial dysfunction, focusing on nitric oxide (NO) and oxidative stress pathways. Methods: Four glycomimetics were synthesized by the stepwise transformation of 2,5dihydroxybenzoic acid to a range of 2,5substituted benzoic acid derivatives, incorporating the key sulfate groups to mimic the interactions of heparan sulfate. Endothelial function was assessed using acetylcholineinduced, endotheliumdependent relaxation in mouse thoracic aortic rings using wire myography. Human umbilical vein endothelial cell (HUVEC) behavior was evaluated in the presence or absence of the free fatty acid, palmitate, with or without glycomimetics (1µM). DAF2 and H2DCFDA assays were used to determine nitric oxide (NO) and reactive oxygen species (ROS) production, respectively. Lipid peroxidation colorimetric and antioxidant enzyme activity assays were also carried out. RTPCR and western blotting were utilized to measure Akt, eNOS, Nrf2, NQO1 and HO1 expression. Results: Ex vivo endotheliumdependent relaxation was significantly improved by the glycomimetics under palmitateinduced oxidative stress. In vitro studies showed that the glycomimetics protected HUVECs against the palmitateinduced oxidative stress and enhanced NO production. We demonstrate that the protective effects of preincubation with glycomimetics occurred via upregulation of Akt/eNOS signaling, activation of the Nrf2/ARE pathway, and suppression of ROSinduced lipid peroxidation. Conclusion: We have developed a novel set of small molecule glycomimetics that protect against free fatty acidinduced endothelial dysfunction and thus, represent a new category of therapeutic drugs to target endothelial damage, the first line of defense against cardiovascular disease
Mechanisms of action of systemic antibiotics used in periodontal treatment and mechanisms of bacterial resistance to these drugs
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