Analyzing the social factors that influence willingness to pay for the management of invasive alien species under two different strategies: eradication and prevention

This an accepted author's manuscript (AAM) version of an article published in Environmental Management, 48 (2011): 418-43

Origin, accumulation and fate of dissolved organic matter in an extreme hypersaline shallow lake

Hypersaline endorheic aquatic systems (H-SEAS) are lakes/shallow playas in arid and semiarid regions that undergo extreme oscillations in salinity and severe drought episodes. Although their geochemical uniqueness and microbiome have been deeply studied, very little is known about the availability and quality of dissolved organic matter (DOM) in the water column. A H-SEAS from the Monegros Desert (Zaragoza, NE Spain) was studied during a hydrological wetting-drying-rewetting cycle. DOM analysis included: (i) a dissolved organic carbon (DOC) mass balance; (ii) spectroscopy (absorbance and fluorescence) and (iii) a molecular characterization with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The studied system stored a large amount of DOC and under the highest salinity conditions, salt-saturated waters (i.e., brines with salinity > 30%) accumulated a disproportionate quantity of DOC, indicating a significant in-situ net DOM production. Simultaneously, during the hydrological transition from wet to dry, the DOM pool showed strong alterations of it molecular composition. Spectroscopic methods indicated that aromatic and degraded DOM was rapidly replaced by fresher, relatively small, microbial-derived moieties with a large C/N ratio. FT-ICR-MS highlighted the accumulation of small, saturated and oxidized molecules (molecular O/C > 0.5), with a remarkable increase in the relative contribution of highly oxygenated (molecular O/C > 0.9) compounds and a decrease of aliphatic and carboxyl-rich alicyclic moleculesThese results indicated that H-SEAS are extremely active in accumulating and processing DOM, with the notable release of organic solutes probably originated from decaying microplankton under large osmotic stress at extremely high salinitie

Are Chinese consumers at risk due to exposure to metals in crayfish? A bioaccessibility-adjusted probabilistic risk assessment

Freshwater crayfish, the world's third largest crustacean species, has been reported to accumulate high levels of metals, while the current knowledge of potential risk associated with crayfish consumption lags behind that of finfish. We provide the first estimate of human health risk associated with crayfish (Procambarus clarkii) consumption in China, the world's largest producer and consumer of crayfish. We performed Monte Carlo Simulation on a standard risk model parameterized with local data on metal concentrations, bioaccessibility (phi), crayfish consumption rate, and consumer body mass. Bioaccessibility of metals in crayfish was found to be variable (68-95%) and metal-specific, suggesting a potential influence of metal bioaccessibility on effective metal intake. However, sensitivity analysis suggested risk of metals via crayfish consumption was predominantly explained by consumption rate (explaining >92% of total risk estimate variability), rather than metals concentration, bioaccessibility, or body mass. Mean metal concentrations (As, Cd, Cu, Ni, Pb, Se and Zn) in surveyed crayfish samples from 12 provinces in China conformed to national safety standards. However, risk calculation of phi-modified hazard quotient (HQ) and hazard index (HI) suggested that crayfish metals may pose a health risk for very high rate consumers, with a HI of over 24 for the highest rate consumers. Additionally, the phi-modified increased lifetime risk (ILTR) for carcinogenic effects due to the presence of As was above the acceptable level (10(-5)) for both the median (ILTR = 2.5 x 10(-5)) and 90th percentile (ILTR = 1.8 x 10(-4)), highlighting the relatively high risk of As in crayfish. Our results suggest a need to consider crayfish when assessing human dietary exposure to metals and associated health risks, especially for high crayfish-consuming populations, such as in China, USA and Sweden.HZ by the National Natural Science Foundation of China (41273087). LN was supported by European Union Marie Curie Actions, Grant FP People 2010 “IRSES Electroacross” and BG by the SAGE-IGERT Fellowship (US National Science Foundation)

Habitat quality affects the condition of Luciobarbus sclateri in the Guadiamar River (SW Iberian Peninsula): Effects of disturbances by the toxic spill of the Aznalcóllar mine

This study analyzes the somatic condition of southern Iberian barbel Luciobarbus sclateri (Günther, 1868) in the Guadiamar River (SW Iberian Peninsula). This river was seriously affected by a toxic spill of about 4 million cubic meters of acidic water and 2 million cubic meters of mud rich in heavy metals. Once the spill removal works concluded, sites affected and unaffected by the accident were sampled to study its effects on the fish fauna. The ecological variables registered were related to water quality, physical state of reaches, ecological quality, resources exploited by fish, and potential intra-specific interactions. From an initial 15 ecological variables, seasonal water flow and pH explained most of the variation in barbel condition. This study shows that the Guadiamar River, 56 months after the accident, is still undergoing a recovery process where, beyond ecological variables, proximity to the affected area is the most influential factor for fish condition. © 2012 Springer Science+Business Media B.V

In Vivo DNA Binding of Bacteriophage GA-1 Protein p6▿

Bacteriophage GA-1 infects Bacillus sp. strain G1R and has a linear double-stranded DNA genome with a terminal protein covalently linked to its 5′ ends. GA-1 protein p6 is very abundant in infected cells and binds DNA with no sequence specificity. We show here that it binds in vivo to the whole viral genome, as detected by cross-linking, chromatin immunoprecipitation, and real-time PCR analyses, and has the characteristics of a histone-like protein. Binding to DNA of GA-1 protein p6 shows little supercoiling dependency, in contrast to the ortholog protein of the evolutionary related Bacillus subtilis phage φ29. This feature is a property of the protein rather than the DNA or the cellular background, since φ29 protein p6 shows supercoiling-dependent binding to GA-1 DNA in Bacillus sp. strain G1R. GA-1 DNA replication is impaired in the presence of the gyrase inhibitors novobiocin and nalidixic acid, which indicates that, although noncovalently closed, the viral genome is topologically constrained in vivo. GA-1 protein p6 is also able to bind φ29 DNA in B. subtilis cells; however, as expected, the binding is less supercoiling dependent than the one observed with the φ29 protein p6. In addition, the nucleoprotein complex formed is not functional, since it is not able to transcomplement the DNA replication deficiency of a φ29 sus6 mutant. Furthermore, we took advantage of φ29 protein p6 binding to GA-1 DNA to find that the viral DNA ejection mechanism seems to take place, as in the case of φ29, with a right to left polarity in a two-step, push-pull process

Binding of phage Φ29 architectural protein p6 to the viral genome: evidence for topological restriction of the phage linear DNA

Bacillus subtilis phage Φ29 protein p6 is required for DNA replication and promotes the switch from early to late transcription. In vivo it binds all along the viral linear DNA, which suggests a global role as an architectural protein; in contrast, binding to bacterial DNA is negligible. This specificity could be due to the p6 binding preference for less negatively supercoiled DNA, as is presumably the case with viral (with respect to bacterial) DNA. Here we demonstrate that p6 binding to Φ29 DNA is greatly increased when negative supercoiling is decreased by novobiocin; in addition, gyrase is required for DNA replication. This indicates that, although non-covalently closed, the viral genome is topologically constrained in vivo. We also show that the p6 binding to different Φ29 DNA regions is modulated by the structural properties of their nucleotide sequences. The higher affinity for DNA ends is possibly related to the presence of sequences in which their bendability properties favor the formation of the p6–DNA complex, whereas the lower affinity for the transcription control region is most probably due to the presence of a rigid intrinsic DNA curvature

Phage φ29 Proteins p1 and p17 Are Required for Efficient Binding of Architectural Protein p6 to Viral DNA In Vivo

Bacteriophage φ29 protein p6 is a viral architectural protein, which binds along the whole linear φ29 DNA in vivo and is involved in initiation of DNA replication and transcription control. Protein p1 is a membrane-associated viral protein, proposed to attach the viral genome to the cell membrane. Protein p17 is involved in pulling φ29 DNA into the cell during the injection process. We have used chromatin immunoprecipitation and real-time PCR to analyze in vivo p6 binding to DNA in cells infected with φ29 sus1 or sus17 mutants; in both cases p6 binding is significantly decreased all along φ29 DNA. φ29 DNA is topologically constrained in vivo, and p6 binding is highly increased in the presence of novobiocin, a gyrase inhibitor that produces a loss of DNA negative superhelicity. Here we show that, in cells infected with φ29 sus1 or sus17 mutants, the increase of p6 binding by novobiocin is even higher than in cells containing p1 and p17, alleviating the p6 binding deficiency. Therefore, proteins p1 and p17 could be required to restrain the proper topology of φ29 DNA, which would explain the impaired DNA replication observed in cells infected with sus1 or sus17 mutants