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1.
Phys Rev Lett ; 132(26): 263602, 2024 Jun 28.
Article in English | MEDLINE | ID: mdl-38996281

ABSTRACT

Solid-state spin qubits are promising candidates for quantum information processing, but controlled interactions and entanglement in large, multiqubit systems are currently difficult to achieve. We describe a method for programmable control of multiqubit spin systems, in which individual nitrogen-vacancy (NV) centers in diamond nanopillars are coupled to magnetically functionalized silicon nitride mechanical resonators in a scanning probe configuration. Qubits can be entangled via interactions with nanomechanical resonators while programmable connectivity is realized via mechanical transport of qubits in nanopillars. To demonstrate the feasibility of this approach, we characterize both the mechanical properties and the magnetic field gradients around the micromagnet placed on the nanobeam resonator. We demonstrate coherent manipulation of a spin qubit in the proximity of a transported micromagnet by utilizing nuclear spin memory and use the NV center to detect the time-varying magnetic field from the oscillating micromagnet, extracting a spin-mechanical coupling of 7.7(9) Hz. With realistic improvements, the high-cooperativity regime can be reached, offering a new avenue toward scalable quantum information processing with spin qubits.

2.
Sci Adv ; 6(38)2020 Sep.
Article in English | MEDLINE | ID: mdl-32938673

ABSTRACT

Glacial lake outburst floods (GLOFs) are a substantial hazard for downstream communities in vulnerable regions, yet unpredictable triggers and remote source locations make GLOF dynamics difficult to measure and quantify. Here, we revisit a destructive GLOF that occurred in Bhutan in 1994 and apply cross-correlation-based seismic analyses to track the evolution of the GLOF remotely (~100 kilometers from the source region). We use the seismic observations along with eyewitness reports and a downstream gauge station to constrain a numerical flood model and then assess geomorphic change and current state of the unstable lakes via satellite imagery. Coherent seismic energy is evident from 1 to 5 hertz beginning approximately 5 hours before the flood impacted Punakha village, which originated at the source lake and advanced down the valley during the GLOF duration. Our analysis highlights potential benefits of using real-time seismic monitoring to improve early warning systems.

3.
Phys Rev Lett ; 124(16): 163604, 2020 Apr 24.
Article in English | MEDLINE | ID: mdl-32383959

ABSTRACT

We demonstrate a new mechanical transduction platform for individual spin qubits. In our approach, single micromagnets are trapped using a type-II superconductor in proximity of spin qubits, enabling direct magnetic coupling between the two systems. Controlling the distance between the magnet and the superconductor during cooldown, we demonstrate three-dimensional trapping with quality factors around 1×10^{6} and kHz trapping frequencies. We further exploit the large magnetic moment to mass ratio of this mechanical oscillator to couple its motion to the spin degrees of freedom of an individual nitrogen vacancy center in diamond. Our approach provides a new path towards interfacing individual spin qubits with mechanical motion for testing quantum mechanics with mesoscopic objects, realization of quantum networks, and ultrasensitive metrology.

4.
Sci Adv ; 5(6): eaav7266, 2019 Jun.
Article in English | MEDLINE | ID: mdl-31223649

ABSTRACT

Himalayan glaciers supply meltwater to densely populated catchments in South Asia, and regional observations of glacier change over multiple decades are needed to understand climate drivers and assess resulting impacts on glacier-fed rivers. Here, we quantify changes in ice thickness during the intervals 1975-2000 and 2000-2016 across the Himalayas, using a set of digital elevation models derived from cold war-era spy satellite film and modern stereo satellite imagery. We observe consistent ice loss along the entire 2000-km transect for both intervals and find a doubling of the average loss rate during 2000-2016 [-0.43 ± 0.14 m w.e. year-1 (meters of water equivalent per year)] compared to 1975-2000 (-0.22 ± 0.13 m w.e. year-1). The similar magnitude and acceleration of ice loss across the Himalayas suggests a regionally coherent climate forcing, consistent with atmospheric warming and associated energy fluxes as the dominant drivers of glacier change.

5.
J Fish Biol ; 92(4): 1090-1109, 2018 Apr.
Article in English | MEDLINE | ID: mdl-29479689

ABSTRACT

Headwater-resident fishes may be prone to a high rate of isolation and a pronounced hierarchical genetic structure due to a combination of niche preference and dendritic effects of river networks. Genetic isolation patterns were compared using microsatellites in six headwater fishes, Fundulus olivaceus, Semotilus atromaculatus, Erimyzon claviformis, Etheostoma artesiae, Etheostoma whipplei and Etheostoma parvipinne, in three geographic regions that included drainages of small, medium and large sizes in the southern United States. All species showed hierarchical nesting of genetic populations and there were clear and mostly consistent differences between species and regions that were identified through summary statistics derived from two independent analyses. For species comparisons, a high isolation grouping (increased number of isolated genetic clusters or sites within regions) and a low-isolation grouping (decreased number of clusters or sites) were identified. Species group placement was related to niche breadth along the river continuum and presumed abundance and variability of preferred microhabitats, with increased headwater specialization among species being associated with placement in the high-isolation grouping. There was a weakly significant positive effect of drainage size on the number of isolated clusters or sites across all species. Regional patterns were shared in two species, with the region containing the smallest drainages having lower rates of isolation in both datasets. This study shows the effects of regional and species characteristics on genetic isolation for headwater species, which are especially prone to isolation due to spatial, dendritic effects of river networks.


Subject(s)
Fundulidae/genetics , Genetics, Population , Perches/genetics , Reproductive Isolation , Animals , Ecosystem , Geography , Microsatellite Repeats , Rivers , United States
6.
Pract Lab Med ; 9: 28-38, 2017 Dec.
Article in English | MEDLINE | ID: mdl-29034304

ABSTRACT

INTRODUCTION: Heart failure is well investigated in adults, but data in children is lacking. To overcome this shortage of reliable data, appropriate bioanalytical assays are required. OBJECTIVES: Development and validation of a bioanalytical assay for the determination of aldosterone concentrations in small sample volumes applicable to clinical studies under Good Clinical Laboratory Practice. METHODS: An immunoassay was developed based on a commercially available enzyme-linked immunosorbent assay and validated according to current bioanalytical guidelines of the EMA and FDA. RESULTS: The assay (range 31.3-1000 pg/mL [86.9-2775 pmol/L]) is characterized by a between-run accuracy from - 3.8% to - 0.8% and a between-run imprecision ranging from 4.9% to 8.9% (coefficient of variation). For within-run accuracy, the relative error was between - 11.1% and + 9.0%, while within-run imprecision ranged from 1.2% to 11.8% (CV). For parallelism and dilutional linearity, the relative error of back-calculated concentrations varied from - 14.1% to + 8.4% and from - 7.4% to + 10.5%, respectively. CONCLUSIONS: The immunoassay is compliant with the bioanalytical guidelines of the EMA and FDA and allows accurate and precise aldosterone determinations. As the assay can run low-volume samples, it is especially valuable for pediatric investigations.

7.
J Immunoassay Immunochem ; 38(6): 579-594, 2017.
Article in English | MEDLINE | ID: mdl-28699839

ABSTRACT

INTRODUCTION: The pharmacotherapy of pediatric patients suffering from heart failure is extrapolated from adults due to missing data in children. OBJECTIVES: Development and validation of a low-volume immunoassay for the reliable determination of renin. EXPERIMENTAL: The immunoassay was validated according to international guidelines. RESULTS: The assay allows the reliable determination of renin in 40 µL plasma within a calibration range of 4-128 pg/mL. Between-run accuracy varied from -3.3 to +3.0% (relative error), while between-run precision ranged from 4.9 to 11.3% (coefficient of variation). CONCLUSION: The low-volume immunoassay facilitates the reliable collection of pharmacodynamic data in children.


Subject(s)
Immunoassay/standards , Pediatrics/methods , Renin/blood , Adult , Child , Female , Healthy Volunteers , Humans
8.
Anim Reprod Sci ; 182: 138-145, 2017 Jul.
Article in English | MEDLINE | ID: mdl-28576677

ABSTRACT

The dilution of ejaculates is a fundamental step for the production of liquid-preserved boar semen. For a long time, it has been recommended to add the extender to the ejaculate. The aim of the present study was to first compare the effect of the position ('center' vs. 'wall') where the extender is added to the semen-mixing cylinder (height 32.5cm; diameter 12.7cm) using an automatic dispenser (n=11). In experiment 2 (n=30), we analyzed the two main dilution methods (extender to the semen ('control') vs. 'reverse'). Experiment 3 was carried out to study the dilution effect on kinematics. In Experiments 1 and 2, the sperm distribution 10min after the dilution and the sperm quality parameters during long-term storage (d1, d3, d5, and d7) were evaluated. In Experiment 3, sperm quality was assessed during short-term storage at 0, 10, 20, 30 and 60min after semen dilution ('control' vs. 'reverse'; n=6). There were no significant differences (P>0.05) between the treatments in the specific response to bicarbonate, mitochondrial activity, membrane status, thermo-resistance or sperm motility immediately after dilution or long-term storage. The sperm distribution was significantly (P=0.029) affected by the dilution method in Experiment 2. In summary, treatment with the extender first, which is used by only a few European boar studs, leads to comparable results in sperm quality during storage and better results in sperm distribution after dilution. This procedure is also less time consuming, less foam formation occurs during the semen dilution and the procedure is more hygienic.


Subject(s)
Insemination, Artificial/veterinary , Semen Analysis , Spermatozoa/physiology , Swine/physiology , Animals , Male
9.
Reprod Domest Anim ; 52(3): 397-402, 2017 Jun.
Article in English | MEDLINE | ID: mdl-28066955

ABSTRACT

To achieve a standardized number of spermatozoa in the final AI dose, varying amounts of extender fluid with a fixed concentration of antimicrobial substances are currently added to boar ejaculates. This practice ignores the different degrees of dilution of the antimicrobials in the end product. In calculating the final concentration of gentamicin in AI doses from 27,538 processed boar ejaculates, we demonstrated varying gentamicin concentrations in the resultant extended boar semen samples. The median concentration was 220.37 mg/L. In 25 of the samples (0.09%), the gentamicin concentration fell below 5 mg/L, which is close to or below the epidemiological cut-off value for many bacteria. We calculated the minimum inhibitory concentration of gentamicin for bacteria isolated from raw and extended ejaculates. Five of the isolates from extended ejaculates exceeded the maximum test concentration of 512 mg/L. As a result, we are presenting an alternative method of boar semen preservation whereby a particular combination of gentamicin concentrate and antibiotic-free extender is incorporated that standardizes the antibiotic concentration in the diluted semen. The addition of standardized antibiotic concentrations did not negatively affect sperm quality when compared to the use of ready-to-use extenders. In conclusion, an end volume-based and standardized addition of gentamicin to boar ejaculates can be a helpful alternative to prevent insufficient dosage of antibiotics in liquid preserved boar semen without affecting semen quality.


Subject(s)
Anti-Bacterial Agents/pharmacology , Gentamicins/pharmacology , Semen Preservation/veterinary , Swine , Animals , Anti-Bacterial Agents/administration & dosage , Dose-Response Relationship, Drug , Gentamicins/administration & dosage , Male , Semen/microbiology , Semen Preservation/methods
10.
Phys Rev Lett ; 116(10): 106802, 2016 Mar 11.
Article in English | MEDLINE | ID: mdl-27015502

ABSTRACT

Using inelastic electron scattering in combination with dielectric theory simulations on differently prepared graphene layers on silicon carbide, we demonstrate that the coupling between the 2D plasmon of graphene and the surface optical phonon of the substrate cannot be quenched by modification of the interface via intercalation. The intercalation rather provides additional modes like, e.g., the silicon-hydrogen stretch mode in the case of hydrogen intercalation or the silicon-oxygen vibrations for water intercalation that couple to the 2D plasmons of graphene. Furthermore, in the case of bilayer graphene with broken inversion symmetry due to charge imbalance between the layers, we observe a similar coupling of the 2D plasmon to an internal infrared-active mode, the LO phonon mode. The coupling of graphene plasmons to vibrational modes of the substrate surface and internal infrared active modes is envisioned to provide an excellent tool for tailoring the plasmon band structure of monolayer and bilayer graphene for plasmonic devices such as plasmon filters or plasmonic waveguides. The rigidity of the effect furthermore suggests that it may be of importance for other 2D materials as well.

11.
Rofo ; 188(4): 359-64, 2016 Apr.
Article in English | MEDLINE | ID: mdl-27002497

ABSTRACT

UNLABELLED: Pediatric imaging has been identified as a key application of combined whole-body PET/MRI. First studies have revealed the clinical feasibility and possible advantages of PET/MRI over PET/CT and MRI. Besides a significant reduction in radiation exposure of about 50 - 75 %, combined whole-body PET/MRI offers the diagnostic advantage of the multiparametric characterization of pathophysiologic processes and helps reduce the number of necessary imaging studies. However, very few studies focusing on pediatric PET/MRI have been published to date. Additional studies are necessary in order to fully appreciate the clinical impact of this novel method. This review article shall summarize the existing literature concerning pediatric PET/MRI and give insight into the practical experience derived from over 160 pediatric PET/MRI examinations that were performed in Tübingen. KEY POINTS: •Combined PET/MR is a promising imaging modality in pediatric oncology. •Using combined PET/MRI, diagnostic radiation exposure of pediatric patients and the number of necessary imaging studies can be reduced. •Further clinical studies are necessary in order to define specific indications for combined PET/MRI in pediatric radiology.


Subject(s)
Image Enhancement/methods , Magnetic Resonance Imaging/methods , Multimodal Imaging/methods , Neoplasms/diagnosis , Positron-Emission Tomography/methods , Adolescent , Child , Child, Preschool , Female , Humans , Infant , Infant, Newborn , Male , Medical Oncology/methods , Pediatrics/methods , Reproducibility of Results , Sensitivity and Specificity
12.
Genes Immun ; 17(2): 79-84, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26673963

ABSTRACT

Roquin-1 (Rc3h1) is an E3 ubiquitin ligase originally discovered in a mutational screen for genetic factors contributory to systemic lupus erythematosus-like symptoms in mice. A single base-pair mutation in the Rc3h1 gene resulted in the manifestation of autoantibody production and sustained immunological inflammation characterized by excessive T follicular helper cell activation and formation of germinal centers. Subsequent studies have uncovered a multifactorial process by which Roquin-1 contributes to the maintenance of immune homeostasis. Through its interactions with partner proteins, Roquin-1 targets mRNAs for decay with inducible costimulator being a primary target. In this review, we discuss newly discovered functions of Roquin-1 in the immune system and inflammation, and in disease manifestation, and discuss avenues of further research. A model is presented for the role of Roquin in health and disease.


Subject(s)
Autoantibodies/biosynthesis , Homeostasis/immunology , Inducible T-Cell Co-Stimulator Protein/genetics , Lupus Erythematosus, Systemic/genetics , RNA-Binding Proteins/genetics , Ubiquitin-Protein Ligases/genetics , Animals , Disease Models, Animal , Gene Expression Regulation , Germinal Center/immunology , Germinal Center/pathology , Homeostasis/genetics , Humans , Immunity, Innate , Inducible T-Cell Co-Stimulator Protein/immunology , Lupus Erythematosus, Systemic/immunology , Lupus Erythematosus, Systemic/pathology , Lymphocyte Activation , Mice , Mutation , RNA-Binding Proteins/immunology , Receptors, Tumor Necrosis Factor/genetics , Receptors, Tumor Necrosis Factor/immunology , Signal Transduction , T-Lymphocytes, Helper-Inducer/immunology , T-Lymphocytes, Helper-Inducer/pathology , Ubiquitin-Protein Ligases/immunology
13.
Chemistry ; 21(39): 13696-702, 2015 Sep 21.
Article in English | MEDLINE | ID: mdl-26264355

ABSTRACT

Ion-like ethylzinc(II) compounds with weakly coordinating aluminates [Al(OR(F))4](-) and [(R(F)O)3Al-F-Al(OR(F))3](-) (R(F)=C(CF3)3) were synthesized in a one-pot reaction and fully characterized by single-crystal X-ray diffraction, NMR and vibrational spectroscopy, and by quantum chemical calculations. The catalytic activity of ion-like Et-Zn[Al(OR(F))4] in intermolecular hydroamination and in the unusual double hydroamination of anilines and alkynes was investigated. Favorable performance was also found in comparison to the Et2Zn/[PhNMe2H](+)[B(C6F5)4](-) system generated in situ at lower catalyst loadings of 2.5 mol %.

14.
Eur J Neurol ; 22(11): 1429-35, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26204918

ABSTRACT

Myofibrillar myopathies are a genetically diverse group of skeletal muscle disorders, with distinctive muscle histopathology. Causative mutations have been identified in the genes MYOT, LDB3, DES, CRYAB, FLNC, BAG3, DNAJB6, FHL1, PLEC and TTN, which encode proteins which either reside in the Z-disc or associate with the Z-disc. Mitochondrial abnormalities have been described in muscle from patients with a myofibrillar myopathy. We reviewed the literature to determine the extent of mitochondrial dysfunction in each of the myofibrillar myopathy subtypes. Abnormal mitochondrial distribution is a frequent finding in each of the subtypes, but a high frequency of COX-negative or ragged red fibres, a characteristic finding in some of the conventional mitochondrial myopathies, is a rare finding. Few in vitro studies of mitochondrial function have been performed in affected patients.


Subject(s)
Mitochondria/pathology , Humans , Myopathies, Structural, Congenital/classification , Myopathies, Structural, Congenital/genetics , Myopathies, Structural, Congenital/pathology
15.
J Fish Biol ; 85(5): 1726-32, 2014 Nov.
Article in English | MEDLINE | ID: mdl-25123486

ABSTRACT

A total of 17 polymorphic microsatellite loci were isolated from the blackstripe topminnow Fundulus notatus. In a sample of 29 individuals, these loci were found to possess two to 19 alleles with expected heterozygosity values ranging from 0.212 to 0.919 and all but one of the loci conformed to Hardy-Weinberg equilibrium expectations. Many of these loci were polymorphic in the closely related species Fundulus olivaceus and Fundulus euryzonus providing a set of markers that should prove useful in future ecological and evolutionary studies of members of this species complex.


Subject(s)
Cyprinidae/genetics , Microsatellite Repeats , Alleles , Animals , Genetic Loci , Sequence Analysis, DNA
16.
Genes Brain Behav ; 13(7): 618-25, 2014 Sep.
Article in English | MEDLINE | ID: mdl-24902721

ABSTRACT

Substance use often starts in adolescence and poses a major problem for society and individual health. The dopamine system plays a role in substance use, and catechol-O-methyltransferase (COMT) is an important enzyme that degrades dopamine. The Val(108/158) Met polymorphism modulates COMT activity and thus dopamine levels, and has been linked to substance use. COMT gene methylation, on the other hand, may affect expression and thus indirectly COMT activity. We investigated whether methylation of the COMT gene was associated with adolescents' substance use. Furthermore, we explored whether the COMT Val(108/158) Met polymorphism interacts with COMT gene methylation in association with substance use. In 463 adolescents (mean age=16, 50.8% girls), substance use (cigarette smoking, alcohol and cannabis use) was assessed with self-report questionnaires. From blood samples, COMT Val(108/158) Met genotype and methylation rates of membrane bound (MB) and soluble (S) COMT promoters were assessed. MB-COMT promoter methylation was associated with non-daily smoking [odds ratio (OR)=1.82, P=0.03], but not with daily smoking (OR=1.20, P=0.34), MB-COMT promoter methylation was not associated with alcohol use. Adolescents with the Met/Met genotype and high rates of MB-COMT promoter methylation were less likely to be high-frequent cannabis users than adolescents with the Val/Val or Val/Met genotype. S-COMT promoter methylation was not associated with substance use. These results indicate that there is an association between substance use and COMT gene methylation. Although this association is complex, combining genetic and epigenetic variation of the COMT gene may be helpful in further elucidating the influence of the dopamine system on substance use in adolescence.


Subject(s)
Alcohol Drinking/genetics , Catechol O-Methyltransferase/genetics , DNA Methylation , Marijuana Smoking/genetics , Smoking/genetics , Adolescent , Case-Control Studies , Female , Humans , Male , Polymorphism, Single Nucleotide , Promoter Regions, Genetic
17.
Internist (Berl) ; 55(5): 601-6, 2014 May.
Article in German | MEDLINE | ID: mdl-24770979

ABSTRACT

Guidelines for the reduction of cholesterol to prevent atherosclerotic vascular events were recently released by the American Heart Association and the American College of Cardiology. The authors claim to refer entirely to evidence from randomized controlled trials, thereby confining their guidelines to statins as the primary therapeutic option. The guidelines derived from these trials do not specify treatment goals, but refer to the percentage of cholesterol reduction by statin medication with low, moderate, and high intensity. However, these targets are just as little tested in randomized trials as are the cholesterol goals derived from clinical experience. The same applies to the guidelines of the four patient groups which are defined by vascular risk. No major statin trial has included patients on the basis of their global risk; thus the allocation criteria are also arbitrarily chosen. These would actually lead to a significant increase in the number of patients to be treated with high or maximum dosages of statins. Also, adhering to dosage regulations instead of cholesterol goals contradicts the principles of individualized patient care. The option of the new risk score to calculate lifetime risk up to the age of 80 years in addition to the 10-year risk can be appreciated. Unfortunately it is not considered in the therapeutic recommendations provided, despite evidence from population and genetic studies showing that even a moderate lifetime reduction of low-density lipoprotein (LDL) cholesterol or non-HDL cholesterol has a much stronger effect than an aggressive treatment at an advanced age. In respect to secondary prevention, the new American guidelines broadly match the European guidelines. Thus, the involved societies from Germany, Austria and Switzerland recommend continuing according to established standards, such as the EAS/ESC guidelines.


Subject(s)
Anticholesteremic Agents/administration & dosage , Atherosclerosis/blood , Atherosclerosis/prevention & control , Diet Therapy/standards , Hypercholesterolemia/blood , Hypercholesterolemia/prevention & control , Practice Guidelines as Topic , Austria , Cardiology/standards , Humans , Risk Factors , Switzerland
18.
Science ; 343(6174): 999-1001, 2014 Feb 28.
Article in English | MEDLINE | ID: mdl-24557837

ABSTRACT

Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet, has been undergoing rapid thinning and retreat for the past two decades. We demonstrate, using glacial-geological and geochronological data, that Pine Island Glacier (PIG) also experienced rapid thinning during the early Holocene, around 8000 years ago. Cosmogenic (10)Be concentrations in glacially transported rocks show that this thinning was sustained for decades to centuries at an average rate of more than 100 centimeters per year, which is comparable with contemporary thinning rates. The most likely mechanism was a reduction in ice shelf buttressing. Our findings reveal that PIG has experienced rapid thinning at least once in the past and that, once set in motion, rapid ice sheet changes in this region can persist for centuries.


Subject(s)
Ice Cover , Islands , Beryllium/analysis , Motion , Radioisotopes/analysis
19.
Prev Sci ; 15(4): 557-69, 2014 Aug.
Article in English | MEDLINE | ID: mdl-23609793

ABSTRACT

Representative surveys indicate that eating disorders are an increasing problem, especially among (pre)adolescents. We assessed the effects of a German school-based primary prevention program ("Torera") for seventh graders. Torera especially relates to pathological eating behavior in the realm of bulimia nervosa or binge eating disorder. The program is built upon two previously evaluated modules for sixth graders with a gender-specific adaption. The coeducational intervention involves nine manual-guided lessons touching a wide range of eating-related problems. Twenty-two Thuringian secondary schools (n = 256 boys and 277 girls, aged 11-13 years at baseline) participated in a trial with 2 control groups (untreated and pretreated) with pre-post assessment. Primary outcomes were conspicuous eating behavior and body self-esteem, measured by standardized questionnaires (SCOFF, EAT-26D, and FBeK). Girls and students at risk showed significant improvement with small (d = 0.35) to medium (d = 0.66) effect sizes on eating behavior, significantly mediated by body self-esteem. Boys only improved with respect to eating attitudes, revealing a small effect size (d = 0.35). With relatively low implementation costs (about 2.50 per student), Torera provides an efficient model for reducing risky eating behavior and strengthening body self-esteem without negative side effects. To improve the effectiveness of the intervention, further research efforts focusing on at-risk groups (secondary prevention) and structural actions for prevention (e.g., offering healthy school catering) are needed.


Subject(s)
Feeding and Eating Disorders/prevention & control , Risk Reduction Behavior , Adolescent , Attitude to Health , Child , Feeding and Eating Disorders/psychology , Female , Germany , Humans , Male
20.
Environ Microbiol Rep ; 6(5): 441-7, 2014 Oct.
Article in English | MEDLINE | ID: mdl-25646534

ABSTRACT

The corrinoid protein, HgcA has been shown to be essential for Hg methylation in anaerobic bacteria. We investigated the diversity of hgcA from temperate and tropical wetland soils where Hg methylation is demonstrated. Sequences obtained from both environments clustered with those from the δ-Proteobacteria, Chloroflexi and Methanomicrobia with significant overlap in hgcA phylogeny between libraries. Clear differences in hgcA distribution were observed between two highly contrasting sites within a tropical wetland in Everglades National Park, USA. hgcA sequences obtained from the northern site clustered primarily with those of methanogens, while sequences from the estuarine site clustered primarily with sulphate-reducing bacteria and syntrophs in the δ-Proteobacteria. Libraries obtained from soils collected from a temperate swamp in Sweden were dominated by hgcA sequences within the δ-Proteobacteria with hgcA sequences clustering primarily with iron reducers in the upstream portion of the swamp and with sulphate reducers in the downstream portion of the swamp. Interestingly, enrichments prepared from the lower portion of this temperate wetland contained a high abundance of hgcA sequences clustering with methanogens. This first report on hgcA diversity in environmental samples suggests a role in Hg methylation for various phenotypic groups in different portions of wetlands.


Subject(s)
Bacteria/genetics , Bacterial Proteins/genetics , Mercury/metabolism , Soil Microbiology , Bacteria/classification , Bacteria/isolation & purification , Bacteria/metabolism , Bacterial Proteins/metabolism , Methylation , Molecular Sequence Data , Phylogeny , Wetlands
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