Multidisciplinary characterization of U(VI) sequestration by Acidovorax facilis for bioremediation purposes

The contamination of the environment by U may affect plant life and consequently may have an impact on animal and human health. The present work describes U(VI) sequestration by Acidovorax facilis using a multidisciplinary approach combining wet chemistry, transmission electron microscopy, and spectroscopy methods (e.g. cryo-time resolved laser-induced fluorescence spectroscopy, extended X-ray absorption fine structure spectroscopy, and in-situ attenuated total reflection Fourier transform infrared spectroscopy). This bacterial strain is widely distributed in nature including U-contaminated sites. In kinetic batch experiments cells of A. facilis were contacted for 5 min to 48 h with 0.1 mM U(VI). The results show that the local coordination of U species associated with the cells depends upon time contact. U is bound mainly to phosphate groups of lipopolysaccharide (LPS) at the outer membrane within the first hour. And, that both, phosphoryl and carboxyl functionality groups of LPS and peptidoglycan of A. facilis cells may effectuate the removal of high U amounts from solution at 24-48 h of incubation. It is clearly demonstrated that A. facilis may play an important role in predicting the transport behaviour of U in the environment and that the results will contribute to the improvement of bioremediation methods of U-contaminated sites.

NMR-based structural analysis of the complete rough-type lipopolysaccharide isolated from Capnocytophaga canimorsus

We here describe the NMR analysis of an intact lipopolysaccharide (LPS, endotoxin) in water with 1,2-dihexanoyl-sn-glycero-3-phosphocholine as detergent. When HPLC-purified rough-type LPS of Capnocytophaga canimorsus was prepared, (13)C,(15)N labeling could be avoided. The intact LPS was analyzed by homonuclear ((1)H) and heteronuclear ((1)H,(13)C, and (1)H,(31)P) correlated one- and two-dimensional NMR techniques as well as by mass spectrometry. It consists of a penta-acylated lipid A with an α-linked phosphoethanolamine attached to C-1 of GlcN (I) in the hybrid backbone, lacking the 4'-phosphate. The hydrophilic core oligosaccharide was found to be a complex hexasaccharide with two mannose (Man) and one each of 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo), Gal, GalN, and l-rhamnose residues. Position 4 of Kdo is substituted by phosphoethanolamine, also present in position 6 of the branched Man(I) residue. This rough-type LPS is exceptional in that all three negative phosphate residues are "masked" by positively charged ethanolamine substituents, leading to an overall zero net charge, which has so far not been observed for any other LPS. In biological assays, the corresponding isolated lipid A was found to be endotoxically almost inactive. By contrast, the intact rough-type LPS described here expressed a 20,000-fold increased endotoxicity, indicating that the core oligosaccharide significantly contributes to the endotoxic potency of the whole rough-type C. canimorsus LPS molecule. Based on these findings, the strict view that lipid A alone represents the toxic center of LPS needs to be reassessed.

Identification of the flagellin glycosylation system in Burkholderia cenocepacia and the contribution of glycosylated flagellin to evasion of human innate immune responses

Burkholderia cenocepacia is an opportunistic pathogen threatening patients with cystic fibrosis. Flagella are required for biofilm formation, as well as adhesion to and invasion of epithelial cells. Recognition of flagellin via the Toll-like receptor 5 (TLR5) contributes to exacerbate B. cenocepacia-induced lung epithelial inflammatory responses. In this study, we report that B. cenocepacia flagellin is glycosylated on at least 10 different sites with a single sugar, 4,6-dideoxy-4-(3-hydroxybutanoylamino)-D-glucose. We have identified key genes that are required for flagellin glycosylation, including a predicted glycosyltransferase gene that is linked to the flagellin biosynthesis cluster and a putative acetyltransferase gene located within the O-antigen lipopolysaccharide cluster. Another O-antigen cluster gene, rmlB, which is required for flagellin glycan and O-antigen biosynthesis, was essential for bacterial viability, uncovering a novel target against Burkholderia infections. Using glycosylated and nonglycosylated purified flagellin and a cell reporter system to assess TLR5-mediated responses, we also show that the presence of glycan in flagellin significantly impairs the inflammatory response of epithelial cells. We therefore suggest that flagellin glycosylation reduces recognition of flagellin by host TLR5, providing an evasive strategy to infecting bacteria.

Paediatric community-acquired septic shock: results from the REPEM network study

INTRODUCTION AND PURPOSE OF THE STUDY: With this study we aimed to describe a "true world" picture of severe paediatric 'community-acquired' septic shock and establish the feasibility of a future prospective trial on early goal-directed therapy in children. During a 6-month to 1-year retrospective screening period in 16 emergency departments (ED) in 12 different countries, all children with severe sepsis and signs of decreased perfusion were included.

RESULTS

A 270,461 paediatric ED consultations were screened, and 176 cases were identified. Significant comorbidity was present in 35.8 % of these cases. Intensive care admission was deemed necessary in 65.7 %, mechanical ventilation in 25.9 % and vasoactive medications in 42.9 %. The median amount of fluid given in the first 6 h was 30 ml/kg. The overall mortality in this sample was 4.5 %. Only 1.2 % of the survivors showed a substantial decrease in Paediatric Overall Performance Category (POPC). 'Severe' outcome (death or a decrease ≥2 in POPC) was significantly related (p < 0.01) to: any desaturation below 90 %, the amount of fluid given in the first 6 h, the need for and length of mechanical ventilation or vasoactive support, the use of dobutamine and a higher lactate or lower base excess but not to any variables of predisposition, infection or host response (as in the PIRO (Predisposition, Infection, Response, Organ dysfunction) concept).

CONCLUSION

The outcome in our sample was very good. Many children received treatment early in their disease course, so avoiding subsequent intensive care. While certain variables predispose children to become septic and shocked, in our sample, only measures of organ dysfunction and concomitant treatment proved to be significantly related with outcome. We argue why future studies should rather be large multinational prospective observational trials and not necessarily randomised controlled trials.

Systematic review and validation of prediction rules for identifying children with serious infections in emergency departments and urgent-access primary care

BACKGROUND

Although the vast majority of children with acute infections are managed at home, this is one of the most common problems encountered in children attending emergency departments (EDs) and primary care. Distinguishing children with serious infection from those with minor or self-limiting infection is difficult. This can result in misdiagnosis of children with serious infections, which results in a poorer health outcome, or a tendency to refer or admit children as a precaution; thus, inappropriately utilising secondary-care resources.

OBJECTIVES

We systematically identified clinical features and laboratory tests which identify serious infection in children attending the ED and primary care. We also identified clinical prediction rules and validated those using existing data sets.

DATA SOURCES

We searched MEDLINE, Medion, EMBASE, Cumulative Index to Nursing and Allied Health Literature and Database of Abstracts of Reviews of Effects in October 2008, with an update in June 2009, using search terms that included terms related to five components: serious infections, children, clinical history and examination, laboratory tests and ambulatory care settings. We also searched references of included studies, clinical content experts, and relevant National Institute for Health and Clinical Excellence guidelines to identify relevant studies. There were no language restrictions. Studies were eligible for inclusion if they were based in ambulatory settings in economically developed countries.

REVIEW METHODS

Literature searching, selection and data extraction were carried out by two reviewers. We assessed quality using the quality assessment of diagnostic accuracy studies (QUADAS) instrument, and used spectrum bias and validity of the reference standard as exclusion criteria. We calculated the positive likelihood ratio (LR+) and negative likelihood ratio (LR-) of each feature along with the pre- and post-test probabilities of the outcome. Meta-analysis was performed using the bivariate method when appropriate. We externally validated clinical prediction rules identified from the systematic review using existing data from children attending ED or primary care.

RESULTS

We identified 1939 articles, of which 35 were selected for inclusion in the review. There was only a single study from primary care; all others were performed in the ED. The quality of the included studies was modest. We also identified seven data sets (11,045 children) to use for external validation. The most useful clinical features for ruling in serious infection was parental or clinician overall concern that the illness was different from previous illnesses or that something was wrong. In low- or intermediate-prevalence settings, the presence of fever had some diagnostic value. Additional red flag features included cyanosis, poor peripheral circulation, rapid breathing, crackles on auscultation, diminished breath sounds, meningeal irritation, petechial rash, decreased consciousness and seizures. Procalcitonin (LR+ 1.75-2.96, LR- 0.08-0.35) and C-reactive protein (LR+ 2.53-3.79, LR- 0.25-0.61) were superior to white cell counts. The best performing clinical prediction rule was a five-stage decision tree rule, consisting of the physician's gut feeling, dyspnoea, temperature ≥ 40 °C, diarrhoea and age. It was able to decrease the likelihood of serious infections substantially, but on validation it provided good ruling out value only in low-to-intermediate-prevalence settings (LR- 0.11-0.28). We also identified and validated the Yale Observation Scale and prediction rules for pneumonia, meningitis and gastroenteritis.

LIMITATIONS

Only a single study was identified from primary-care settings, therefore results may lack generalisability.

CONCLUSIONS

Several clinical features are useful to increase or decrease the probability that a child has a serious infection. None is sufficient on its own to substantially raise or lower the risk of serious infection. Some are highly specific ('red flags'), so when present should prompt a more thorough or repeated assessment. C-reactive protein and procalcitonin demonstrate similar diagnostic characteristics and are both superior to white cell counts. However, even in children with a serious infection, red flags will occur infrequently, and their absence does not lower the risk. The diagnostic gap is currently filled by using clinical 'gut feeling' and diagnostic safety-netting, which are still not well defined. Although two prediction rules for serious infection and one for meningitis provided some diagnostic value, we do not recommend widespread implementation at this time. Future research is needed to identify predictors of serious infection in children in primary-care settings, to validate prediction rules more widely, and determine the added value of blood tests in primary-care settings.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

A new uranyl benzoate species characterized by different spectroscopic techniques

For the first time in the aqueous phase the existence of a U(VI)-benzoate complex with a 1:2 stoichiometry could be proven. Using UV-Vis spectroscopy and especially cryo time-resolved laser-induced fluorescence spectroscopy (TRLFS) it was possible to characterize this complex in detail.

Room temperature TRLFS measurements revealed a static as well as a dynamic ligand-initiated quench process in the U(VI)-benzoic acid system. At these conditions no luminescence emission resulting from complex formation was found. Consequently cryo TRLFS was applied to increase the maximum detectable benzoate:U(VI) ratio. By this for the first time a luminescence spectrum of the 1:2 U(VI)-benzoate complex could be determined. This species is characterized by emission bands at 467, 485, 505, 526, and 550 nm which are blue-shifted compared to the ones of the UO2 2+ ion. The luminescence lifetime of the 1:2 complex amounts to 9.21±0.01 μs at −18 ºC compared to 150.4±0.5 μs for UO2 2+.

The stability constant of the newly found species log β 120 has been calculated to be 4.48±0.24. The stability constant of the 1:1 complex was validated to amount to 2.64±0.19. UV-Vis spectroscopy combined with factor analysis yielded the molar absorption spectrum of the 1:2 U(VI)-benzoate species which is characterized by absorption bands at 406, 418, 432.5, 447, and 461 nm and a molar absorption coefficient of 22 L mol−1 cm−1.

Aqueous curium(III) phosphate species characterized by time-resolved laser-induced fluorescence spectroscopy

The formation of aqueous Cm(III) phosphate complexes was studied at room temperature by time-resolved laser-induced fluorescence spectroscopy (TRLFS) in 0.1 M NaClO4 solutions. The experiments were perfomed at a fixed total Cm(III) concentration of 3 × 107 or 2 × 108 M by varying the phosphoric acid concentration (3 × 105–0.1 M) and the pH (1.4–6.0). The red shift of the excitation and emission spectra, as well as the increase of luminescence lifetimes clearly showed the influence of phosphate on the aqueous Cm(III) speciation. In acidic phosphate solutions ([H3PO4] ≤0.1 M, pH 1.4–2.6) an increase in luminescence intensity was detected due to complexation with H2PO4 −. At [H3PO4] ≥4 × 104 M and between pH 4.0 and 6.0 in general a decrease in luminescence intensity affiliates the complexation with HPO4 2−. Two Cm(III)-phosphate complexes could be identified from the emission data, CmH2PO4 2+ and CmHPO4 +, having peak maxima at 599.6 and 600.8 nm, respectively. TRLFS in combination with ultra-filtration (1 kD) showed that the formation of CmHPO4 + is accompanied by the generation of Cm(III)-phosphate colloids especially at [H3PO4] ≥0.002 M and pH ≥ 5. Cm(III)-phosphate colloids formed at pH 5 and 6 are characterized by an emission maximum at 603.1 nm. Based on the factor analysis of the emission data the stability constants of the two complexes were calculated to be log β 121 = 20.23 ± 0.13 and log β 111 = 16.54 ± 0.80 at an ionic strength of 0.1 M (NaClO4).

Unusual outer membrane lipid composition of the gram-negative, lipopolysaccharide-lacking myxobacterium Sorangium cellulosum So ce56

The gram-negative myxobacterium Sorangium cellulosum So ce56 bears the largest bacterial genome published so far, coding for nearly 10,000 genes. Careful analysis of this genome data revealed that part of the genes coding for the very well conserved biosynthesis of lipopolysaccharides (LPS) are missing in this microbe. Biochemical analysis gave no evidence for the presence of LPS in the membranes of So ce56. By analyzing the lipid composition of its outer membrane sphingolipids were identified as the major lipid class, together with ornithine-containing lipids (OL) and ether lipids. A detailed analysis of these lipids resulted in the identification of more than 50 structural variants within these three classes, which possessed several interesting properties regarding to LPS replacement, mediators in myxobacterial differentiation, as well as potential bioactive properties. The sphingolipids with the basic structure C9-methyl-C(20)-sphingosine possessed as an unusual trait C9-methylation, which is common to fungi but highly uncommon to bacteria. Such sphingolipids have not been found in bacteria before, and they may have a function in myxobacterial development. The OL, also identified in myxobacteria for the first time, contained acyloxyacyl groups, which are also characteristic for LPS and might replace those in certain functions. Finally, the ether lipids may serve as biomarkers in myxobacterial development.

Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution

The complex formation in the binary uranium(VI)-glycolate, -α-hydoxyisobutyrate, -α-aminoisobutyrate systems in 1.0 M NaClO4 medium was studied by means of UV-vis, TRLFS, and EXAFS. An increase in absorption and a red shift of the spectra, 5 nm compared to the free UO2 2+, indicate a complex formation between UO2 2+ and α-substituted carboxylic acids already at pH 2. 1:1 complexes dominate the uranyl speciation in the glycolate, α-hydoxyisobutyrate, and α-aminoisobutyrate system at pH 2 and 3, respectively. At higher ligand concentrations a 1:2 complex between UO2 2+ and α-aminoisobutyric acid was observed. There is a very strong quenching of the U(VI) fluorescence in theuranyl–α-hydroxycarboxylate systems that can be quantitatively described by the Stern–Volmer equation. As a result of the strong quenching it is not possible to detect fluorescence spectra for these complexes using TRLFS. The UO2 2+(aq) concentration calculated from the Stern–Volmer equation was used to determine equilibrium constants which are in good agreement with those obtained by potentiometry and NMR spectroscopy. No quenching was observed in the α-aminoisobutyrate system and their fluorescence spectra could be deconvoluted into components for the different species present. The following stability constants result from our TRLFS experiments: a) for the glycolate system log β UO₂(HOCH₂COO)⁺=2.52±0.20, b) for the α-hydroxyisobutyrate system log β UO₂[HOC(CH₃)₂COO]⁺=3.40±0.21, and c) for the α-aminoisobutyrate system logβUO₂[NH₃C(CH₃)₂COO]²⁺=1.30±0.10 and log β UO₂[NH₃C(CH₃)₂COO]₂²⁺=2.07±0.25. An increase of the fluorescence intensity connected with a red shift of the fluorescence emission spectra was observed in the system uranyl–α-aminoisobutyric acid. Fluorescence lifetimes and spectra were obtained for UO2 2+, UO2[NH3C(CH3)2COO]2+, and UO2[NH3C(CH3)2COO]2 2+. Uranium L III-edge EXAFS measurements yielded an U-Oeq distance of 2.40 to 2.43 Å in the pH range from 2 to 4 in the α-hydroxyisobutyrate system showing a dominant bidentate coordination via the oxygens of the carboxylic group. Slightly shorter U-Oeq distances of 2.40 to 2.38 Å and no evidence for U-C distances around 2.90 Å in the glycolate system in this pH range may indicate a monodentate coordinated ligand via one oxygen from the carboxylic group. The decrease in the U-Oeq distance of the equatorial oxygens in both systems to 2.36-2.37 Å at pH values ≥5 is a strong indication for the formation of a chelate complex due to the deprotonation of the α-OH-group of the ligand. In the glycolate system in the pH range 5.5 to 11, the EXAFS spectrum showed evidence of U-U interaction at 3.81 Å indicating the formation of dimeric species.

The hydrolysis of dioxouranium(VI) investigated using EXAFS and17O-NMR

The structure of dioxouranium(VI) as a function of pH at different (CH3)4N-OH concentrations has been investigated with the aid of U LIII-edge EXAFS. Polynuclear hydroxo species were identified by an U-U interaction at 3.808Å at pH = 4.1. The precipitate formed at pH = 7 has a schoepite like structure. In solution at high pH [0.5 M (CH3)4N-OH], the EXAFS data are consistent with the formation of a monomeric four coordinated uranium(VI) hydroxide complex UO2(OH)42-of octahedral geometry. The first shell contains two O atoms with a U=O distance of 1.830Å, and four O atoms were identified at a U-O distance of 2.265Å.

In strong alkaline solutions [>1 M (CH3)4N)-OH],17O-NMR spectra indicate the presence of two species, presumably UO2(OH)42-and UO2(OH)53-, the latter in low concentration, which are in rapid equilibrium with one another at 268 K in aqueous solution.