Multiple mechanisms of uranium immobilization by Cellulomonas sp. strain ES6

Removal of hexavalent uranium (U(VI)) from aqueous solution was studied using a Gram‐positive facultative anaerobe, Cellulomonas sp. strain ES6, under anaerobic, non‐growth conditions in bicarbonate and PIPES buffers. Inorganic phosphate was released by cells during the experiments providing ligands for formation of insoluble U(VI) phosphates. Phosphate release was most probably the result of anaerobic hydrolysis of intracellular polyphosphates accumulated by ES6 during aerobic growth. Microbial reduction of U(VI) to U(IV) was also observed. However, the relative magnitudes of U(VI) removal by abiotic (phosphate‐based) precipitation and microbial reduction depended on the buffer chemistry. In bicarbonate buffer, X‐ray absorption fine structure (XAFS) spectroscopy showed that U in the solid phase was present primarily as a non‐uraninite U(IV) phase, whereas in PIPES buffer, U precipitates consisted primarily of U(VI)‐phosphate. In both bicarbonate and PIPES buffer, net release of cellular phosphate was measured to be lower than that observed in U‐free controls suggesting simultaneous precipitation of U and PO. In PIPES, U(VI) phosphates formed a significant portion of U precipitates and mass balance estimates of U and P along with XAFS data corroborate this hypothesis. High‐resolution transmission electron microscopy (HR‐TEM) and energy dispersive X‐ray spectroscopy (EDS) of samples from PIPES treatments indeed showed both extracellular and intracellular accumulation of U solids with nanometer sized lath structures that contained U and P. In bicarbonate, however, more phosphate was removed than required to stoichiometrically balance the U(VI)/U(IV) fraction determined by XAFS, suggesting that U(IV) precipitated together with phosphate in this system. When anthraquinone‐2,6‐disulfonate (AQDS), a known electron shuttle, was added to the experimental reactors, the dominant removal mechanism in both buffers was reduction to a non‐uraninite U(IV) phase. Uranium immobilization by abiotic precipitation or microbial reduction has been extensively reported; however, the present work suggests that strain ES6 can remove U(VI) from solution simultaneously through precipitation with phosphate ligands and microbial reduction, depending on the environmental conditions. Cellulomonadaceae are environmentally relevant subsurface bacteria and here, for the first time, the presence of multiple U immobilization mechanisms within one organism is reported using Cellulomonas sp. strain ES6. Biotechnol. Bioeng. 2011;108: 264–276. © 2010 Wiley Periodicals, Inc.     

Identification of low-frequency TRAF3IP2 coding variants in psoriatic arthritis patients and functional characterization

Introduction

In recent genome-wide association studies for psoriatic arthritis (PsA) and psoriasis vulgaris, common coding variants in the TRAF3IP2 gene were identified to contribute to susceptibility to both disease entities. The risk allele of p.Asp10Asn (rs33980500) proved to be most significantly associated and to encode a mutant protein with an almost completely disrupted binding property to TRAF6, supporting its impact as a main disease-causing variant and modulator of IL-17 signaling.

Methods

To identify further variants, exons 2-4 encoding both known TNF-receptor-associated factor (TRAF) binding domains were sequenced in 871 PsA patients. Seven missense variants and one three-base-pair insertion were identified in 0.06% to 1.02% of alleles. Five of these variants were also present in 931 control individuals at comparable frequency. Constructs containing full-length wild-type or mutant TRAF3IP2 were generated and used to analyze functionally all variants for TRAF6-binding in a mammalian two-hybrid assay.

Results

None of the newly found alleles, though, encoded proteins with different binding properties to TRAF6, or to the cytoplasmic tail of the IL-17-receptor α-chain, suggesting that they do not contribute to susceptibility.

Conclusions

Thus, the TRAF3IP2-variant p.Asp10Asn is the only susceptibility allele with functional impact on TRAF6 binding, at least in the German population.     

Serum and Cerebrospinal Fluid Levels of Transthyretin in Lewy Body Disorders with and without Dementia

Parkinson’s disease (PD) without (non-demented, PDND) and with dementia (PDD), and dementia with Lewy bodies (DLB) are subsumed under the umbrella term Lewy body disorders (LBD). The main component of the underlying pathologic substrate, i.e. Lewy bodies and Lewy neurites, is misfolded alpha-synuclein (Asyn), and - in particular in demented LBD patients - co-occurring misfolded amyloid-beta (Abeta). Lowered blood and cerebrospinal fluid (CSF) levels of transthyretin (TTR) - a clearance protein mainly produced in the liver and, autonomously, in the choroid plexus - are associated with Abeta accumulation in Alzheimer’s disease. In addition, a recent study suggests that TTR is involved in Asyn clearance. We measured TTR protein levels in serum and cerebrospinal fluid of 131 LBD patients (77 PDND, 26 PDD, and 28 DLB) and 72 controls, and compared TTR levels with demographic and clinical data as well as neurodegenerative markers in the CSF. Five single nucleotide polymorphisms of the TTR gene which are considered to influence the ability of the protein to carry its ligands were also analyzed. CSF TTR levels were significantly higher in LBD patients compared to controls. Post-hoc analysis demonstrated that this effect was driven by PDND patients. In addition, CSF TTR levels correlated negatively with CSF Abeta_1–42, total tau and phospho-tau levels. Serum TTR levels did not significantly differ among the studied groups. There were no relevant associations between TTR levels and genetic, demographic and clinical data, respectively. These results suggest an involvement of the clearance protein TTR in LBD pathophysiology, and should motivate to elucidate TTR-related mechanisms in LBD in more detail.     

Transition Metal Catalyst-Assisted Reductive Dechlorination of Perchloroethylene by Anaerobic Aquifer Enrichments

Bioremediation of groundwater contaminated with chlorinated solvents, such as perchloroethylene (PCE) or carbon tetrachloride, can be accomplished by adding nutrients to stimulate a microbial community capable of reductive dechlorination. However, biotransformation of these solvents, especially PCE, typically occurs very slowly or not at all. Experiments were conducted to evaluate whether the addition of transition metal tetrapyrrole catalysts would increase the reductive transformation of PCE to trichloroethylene (TCE) by sulfate-reducing enrichment cultures. Batch assays were used to test vitamin B₁₂ and two synthetic sulfonatophenyl porphine catalysts for the stimulation of reductive dechlorination of PCE by sulfate-reducing bacteria (SRB) enriched from aquifer sediments from two locations at Dover Air Force Base. Cells from the enrichments were concentrated and added to batch assay vials. Vials containing SRB cells amended with vitamin B12 exhibited enhanced transformation of PCE to TCE compared with reactors amended with either synthetic catalysts or reactors containing cells alone. Methane production was observed in reactors that exhibited maximum levels of dechlorination. Storage of aquifer sediments between enrichments led to decreased levels of PCE dechlorination in subsequent assays.     

Morphologische und biochemische Untersuchungen zur Wirkung von Barbitursäure,Ureidobernsteinsäure,Orotsäure,Uracil und Thymin auf den diabetogenen Effekt des Alloxans

Zusammenfassung An Ratten wurde mit biochemischen und histologischen Untersuchungsverfahren die Frage überprüft, ob die diabetogene Wirkung des Alloxans etwa durch Verdrängung der Pyrimidinbasen Cytosin, Thymin und Uracil während der Biosynthese von Nucleinsäuren zustandekommt. Dazu wurden diese Substanzen und ihre Vorstufen Orotsäure und Ureidobernsteinsäure sowie (vergleichsweise) Barbitursäure in 4fach so hoher Konzentration wie Alloxan 5 min vor der Applikation des letzteren intraperitoneal injiziert. Es wurden Blutzucker, Serumharnsäure und Leberglykogen bestimmt und mit den histologischen Befunden an Leber, Nebenniere, Niere, Pankreas und Schilddrüse verglichen. Lediglich Orotsäure konnte die Alloxanwirkung auf Blutzucker und Organe bei gleichzeitig selektiver Schädigung der Leber signifikant verhindern. Barbitursäure schwächt zwar die hyperglykämisierende Wirkung des Alloxans stark ab, hat aber keine Schutzfunktion am Pankreas.

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Summary By biochemical and histological methods in rats the question is examined experimentally, if alloxan influences the biosynthesis of nucleid acids by competition of the pyrimidine bases cytosine, thymine and uracil. For this purpose these substances as well as their precursors orotic acid and ureido-succinic acid and (for comparison) barbituric acid were intraperitoneally injected to albino rats in a concentration four times higher than that of alloxan 5 min before the application to the latter. Blood sugar, serum uric acid and liver glycogen were determined and compared with the histological findings in liver, suprarenal gland, kidney, pancreas and thyroid gland. Only orotic acid could prevent significantly the alloxan effect on blood sugar and organs with simultaneous selective damage of liver. Barbituric acid actually diminishes strongly the hyperglycemic action of alloxan, but has no protecting effect on pancreas.

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Mit dankenswerter Unterstützung durch einen Forschungsauftrag des Staatssekretariates für Hochschulwesen der DDR.     

Growth effects and assimilation of organic acids in chemostat and batch cultures of <Emphasis Type="Italic">Acidithiobacillus caldus</Emphasis>

The ability of Acidithiobacillus caldus to grow aerobically using pyruvate, acetate, citrate, 2-ketoglutarate, succinate, and malate as either an electron donor and carbon source (heterotrophic growth), or as a carbon source when potassium tetrathionate was added as an electron donor (mixotrophic growth), was tested in chemostat cultures. Under both heterotrophic and mixotrophic conditions, organic acids were added to a sub-lethal concentration (50 μM). Under mixotrophic conditions, potassium tetrathionate was added to an excess concentration (10 mM). No cell growth was observed under heterotrophic conditions; however, effluent cell concentrations increased over threefold when pyruvate was coupled with potassium tetrathionate. Under these conditions, the effluent pyruvate concentration was reduced to below the detection limit (2 μM), and oxygen consumption increased by approximately 100%. Although pyruvate provided a carbon source in these experiments, ambient carbon dioxide was also available to the cells. To test whether At. caldus could grow mixotrophically using pyruvate as a sole carbon source and potassium tetrathionate as an electron donor, cells were batch cultured in a medium free of dissolved inorganic carbon, and with no carbon dioxide in the headspace. These experiments showed that At. caldus was able to convert between 65 ± 8 and 82 ± 15% of the pyruvate carbon to cellular biomass, depending on the initial pyruvate concentrations. This work is the first to identify a defined organic-carbon source, other than glucose, that At. caldus can assimilate. This has important implications, as mixotrophic and heterotrophic activity has been shown to increase mineral leaching in acidic systems.     

Enhancement of Carotenoid Biosynthesis in Transplastomic Tomatoes by Induced Lycopene-to-Provitamin A Conversion

Carotenoids are essential pigments of the photosynthetic apparatus and an indispensable component of the human diet. In addition to being potent antioxidants, they also provide the vitamin A precursor β-carotene. In tomato (Solanum lycopersicum) fruits, carotenoids accumulate in specialized plastids, the chromoplasts. How the carotenoid biosynthetic pathway is regulated and what limits total carotenoid accumulation in fruit chromoplasts is not well understood. Here, we have introduced the lycopene β-cyclase genes from the eubacterium Erwinia herbicola and the higher plant daffodil (Narcissus pseudonarcissus) into the tomato plastid genome. While expression of the bacterial enzyme did not strongly alter carotenoid composition, expression of the plant enzyme efficiently converted lycopene, the major storage carotenoid of the tomato fruit, into provitamin A (β-carotene). In green leaves of the transplastomic tomato plants, more lycopene was channeled into the β-branch of carotenoid biosynthesis, resulting in increased accumulation of xanthophyll cycle pigments and correspondingly reduced accumulation of the α-branch xanthophyll lutein. In fruits, most of the lycopene was converted into β-carotene with provitamin A levels reaching 1 mg per g dry weight. Unexpectedly, transplastomic tomatoes also showed a >50% increase in total carotenoid accumulation, indicating that lycopene β-cyclase expression enhanced the flux through the pathway in chromoplasts. Our results provide new insights into the regulation of carotenoid biosynthesis and demonstrate the potential of plastids genome engineering for the nutritional enhancement of food crops.Carotenoids are isoprenoid molecules that are synthesized by all photosynthetic organisms and also by some fungi and nonphotosynthetic bacteria. In plants, they participate in photosynthetic light harvesting and protection against light stress. In addition, carotenoids accumulate to large levels as storage metabolites in chromoplasts of flowers, fruits, and taproots. Carotenoids are also essential to animals, which, however, are unable to synthesize them de novo, and therefore must rely on dietary sources of carotenoids. β-Carotene is the main dietary precursor of vitamin A and therefore also referred to as provitamin A. Vitamin A deficiency in humans represents a global health problem affecting approximately one-third of the countries of the world (Mayer et al., 2008). Presumably due to their antioxidant activity, β-carotene and other carotenoid species also exert protective effects against cardiovascular diseases, certain cancers, and aging-related diseases (Collins, 1999).While the enzymology of the carotenoid biosynthetic pathways in plants and eubacteria is now reasonably well understood (Armstrong, 1997; Cunningham and Gantt, 1998; Hirschberg, 2001), understanding of the regulation of carotenoid biosynthesis is still rather poor (Bramley, 2002). Mainly using the tomato (Solanum lycopersicum) fruit as model system, the study of pigmentation mutants (Ronen et al., 2000; Isaacson et al., 2002; Galpaz et al., 2006) and transgenic approaches (Giuliano et al., 2000, 2008; Römer and Fraser, 2005; Fraser et al., 2007) have provided first insights into regulatory mechanisms operating in carotenogenesis. For example, constitutive expression of the phytoene desaturase (crtI) gene from the bacterium Erwinia uredovora resulted in elevated β-carotene accumulation in tomatoes, but also led to an unexpected reduction in total carotenoid levels (Römer et al., 2000). The reduction in total carotenoids is believed to be an effect of feedback regulation from β-carotene or one of its downstream metabolites (Bramley, 2002). However, fruit-specific overexpression of the native lycopene β-cyclase resulted in increased β-carotene accumulation, without a concomitant decrease in total carotenoids (Rosati et al., 2000). Why some genetic disturbances of carotenoid biosynthesis negatively affect total carotenoid accumulation and others do not (or even result in an increase; Dharmapuri et al., 2002; Fraser et al., 2002), remains to be established.Here we have used tomato plastid transformation to address the regulation of carotenoid biosynthesis exerted at the level of lycopene to β-carotene conversion by the enzyme lycopene β-cyclase (Fig. 1A). We show that plastid expression of a plant lycopene β-cyclase does not only trigger efficient conversion of lycopene to β-carotene, but unexpectedly also results in a >50% increase in total carotenoid accumulation. This contrasts moderately increased β-carotene levels and reduced total carotenoid accumulation upon expression of a bacterial lycopene β-cyclase (Wurbs et al., 2007) and suggests lycopene β-cyclase activity as an important regulatory point in plant and microbial carotenoid biosynthesis.Open in a separate windowFigure 1.Engineering of the carotenoid biosynthetic pathway by plastid transformation. A, Carotenoid biosynthetic pathway in higher plants. The pathway splits into an α-branch and a β-branch immediately downstream of lycopene, the major storage carotenoid of tomato fruits. The enzyme expressed from the tomato plastid genome in this study, lycopene β-cyclase, leads into the β-branch. B, Physical maps of the targeting region in the plastid genome (ptDNA) and the plastid transformation vectors pEcrtY and pNLyc constructed in this study. Genes above the line are transcribed from the left to the right, genes below the line are transcribed in the opposite direction. The transgenes are targeted to the intergenic region between the trnfM and trnfG genes (Ruf et al., 2001). The selectable marker gene aadA is driven by a chimeric rRNA operon promoter (Prrn; Svab and Maliga, 1993), fused to the 3′-UTR from the psbA gene (TpsbA), and flanked by two loxP sites to allow marker removal by Cre-mediated site-specific recombination (Zhou et al., 2008). The transgene expression cassette consists of the ribosomal RNA operon promoter fused to the 5′ leader from the gene 10 of phage T7 (Prrn-G10L; Kuroda and Maliga, 2001) and the 3′-UTR of the rps16 gene (Trps16). Restriction sites used for cloning or RFLP analysis are indicated, and the psaB-derived hybridization probe is denoted by a horizontal bar. Sites lost due to ligation to heterologous ends are in parentheses. C, Southern-blot analysis of tomato transplastomic lines carrying the lycopene β-cyclase gene from daffodil (S.l.-pNLyc) or from E. herbicola (S.l.-pEcrtY). Total cellular DNA was digested with BglII and hybridized to a radioactively labeled probe detecting the psaB region of the plastid genome, which flanks the transgene insertion site (section B). Fragment sizes are given in kb. wt, Wild type. D, Alignment (produced with ClustalW2) of the amino acid sequences of the lycopin β-cyclases from daffodil (Np) and E. herbicola (Eh). Asterisk (*) denotes residues identical in both sequences (marked in bold), colon (:) indicates conserved substitutions, and a dot indicates semiconserved substitutions. The N-terminal extension of the Np sequence is likely to harbor the transit peptide for protein import into plastids. The amino acids that changed due to correction of the Lyc sequence from daffodil (published sequence: GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"X98796.1","term_id":"1419692"}}X98796.1; corrected sequence: accession no. {"type":"entrez-nucleotide","attrs":{"text":"GQ327929","term_id":"254681605"}}GQ327929) are underlined. The corrections improve the sequence similarity in the N-terminal domains of the Np and Eh sequences.     

Isolation and characterization of Cr(VI) reducing Cellulomonas spp. from subsurface soils: implications for long-term chromate reduction

Microbial enrichments from Cr(VI) contaminated and uncontaminated US Department of Energy Hanford Site sediments produced Cr(VI) reducing consortia when grown in the presence of Cr(VI) with acetate, D-xylose or glycerol as a carbon and energy source. Eight of the nine isolates from the consortia were Gram positive and four of these were identified by 16S rRNA sequence homology and membrane fatty acid composition as belonging to the genus Cellulomonas. Two strains, ES6 and WS01, were further examined for their ability to reduce Cr(VI) under growth and non-growth conditions. During fermentative growth on D-xylose, ES6 and WS01 decreased aqueous Cr(VI) concentrations from 0.04 mM Cr(VI) to below the detection limit (0.002 mM Cr(VI)) in less than three days and retained their ability to reduce Cr(VI) even after four months of incubation. Washed ES6 and WS01 cells also reduced Cr(VI) under non-growth conditions for over four months, both with and without the presence of an exogenous electron donor. K-edge XANES spectroscopy confirmed the reduction of Cr(VI) to Cr(III). The ability to reduce Cr(VI) after growth had stopped and in the absence of an external electron donor, suggests that stimulation of these types of organisms may lead to effective long-term, in situ passive reactive barriers for Cr(VI) removal. Our results indicate that Cr(VI) reduction by indigenous Cellulomonas spp. may be a potential method of in situ bioremediation of Cr(VI) contaminated sediment and groundwater.     

Polyphenolic Composition and in Vitro Antihypertensive and Anti-Inflammatory Effects of Cuphea lindmaniana and Cuphea urbaniana

The present study investigates the chemical composition, anti-inflammatory, and antihypertensive activities, in vitro, from extracts of Cuphea lindmaniana and Cuphea urbaniana leaves. The extraction was performed ultrasound-assisted, and UHPLC/MS analysis was in positive mode ionization. The anti-inflammatory activity of the extracts and miquelianin were assayed at concentrations 0.001–10 μg/mL by chemotaxis on rat polymorphonuclear neutrophils. The antihypertensive activity was performed by angiotensin-converting enzyme (ACE) inhibition. From the nineteen proposed compounds, six of them are described for the first time in this genus. The extracts displayed antichemotactic effect with a reduction of 100 % of the neutrophil migration, in vitro, in most concentrations. The ACE-inhibition presented results ranging from 19.58 to 22.82 %. In conclusion, C. lindmaniana and C. urbaniana extracts contain a rich diversity of flavonoids and display in vitro anti-inflammatory and antihypertensive potential. Thus, this study could serve as a scientific baseline for further investigation, on developmental novel products with therapeutic actions.