Isolation and Characterization of Mercury Resistant Bacillus sp. from Soils with an Extensive History as Substrates for Mercury Extraction in Mexico

Metal phytoextraction assisted by bacteria plays an important role in bioremediation systems. In this work, mercury-resistant bacterial strains were isolated from soils with high levels of mercury (San Joaquin, Queretaro State, Mexico) and identified as Bacillus sp. based on the 16S rDNA gene sequence analysis. The bacterial strains were found to exhibit different multiple mercury-resistance and carbon source utilization characteristics. The mercury reduction ability was tested through a volatilization assay. The bacterial isolates were also evaluated for their ability to promote growth and mercury uptake in tomato plants. In a roll towel assay, the maximum vigor index of tomato plants was obtained with the inoculation of Bacillus sp. A2, A12, B11, B15 and C1, while in a pot assay, the maximum vigor index was obtained with the inoculation of Bacillus sp. A6, A7 and B20, compared with un-inoculated controls in the presence of HgCl₂. Maximum Hg accumulation in the roots and shoots of tomato plants was obtained only with Bacillus sp. A7 in the roll towel assay, whereas in the pot assay, maximum accumulation was obtained with Bacillus sp. A12 compared with un-inoculated controls. Our results show that mercury accumulation in tissue is enhanced by these plant growth promoting bacterial strains, which recommends their possible use as microbe-assisted phytoremediation systems in mercury-polluted soils.     

Genome-Wide Association Study Implicates Chromosome 9q21.31 as a Susceptibility Locus for Asthma in Mexican Children

Many candidate genes have been studied for asthma, but replication has varied. Novel candidate genes have been identified for various complex diseases using genome-wide association studies (GWASs). We conducted a GWAS in 492 Mexican children with asthma, predominantly atopic by skin prick test, and their parents using the Illumina HumanHap 550 K BeadChip to identify novel genetic variation for childhood asthma. The 520,767 autosomal single nucleotide polymorphisms (SNPs) passing quality control were tested for association with childhood asthma using log-linear regression with a log-additive risk model. Eleven of the most significantly associated GWAS SNPs were tested for replication in an independent study of 177 Mexican case–parent trios with childhood-onset asthma and atopy using log-linear analysis. The chromosome 9q21.31 SNP rs2378383 (p = 7.10×10⁻⁶ in the GWAS), located upstream of transducin-like enhancer of split 4 (TLE4), gave a p-value of 0.03 and the same direction and magnitude of association in the replication study (combined p = 6.79×10⁻⁷). Ancestry analysis on chromosome 9q supported an inverse association between the rs2378383 minor allele (G) and childhood asthma. This work identifies chromosome 9q21.31 as a novel susceptibility locus for childhood asthma in Mexicans. Further, analysis of genome-wide expression data in 51 human tissues from the Novartis Research Foundation showed that median GWAS significance levels for SNPs in genes expressed in the lung differed most significantly from genes not expressed in the lung when compared to 50 other tissues, supporting the biological plausibility of our overall GWAS findings and the multigenic etiology of childhood asthma.     

Conservation genetics of South American aquatic mammals: an overview of gene diversity,population structure,phylogeography, non‐invasive methods and forensics

• 1 Most aquatic mammals have high dispersal potential, and there are often severe conservation concerns related to their legal or illegal harvesting. Therefore, economic, social and forensic factors often arise in decisions relating to their population management. Molecular markers are essential tools in modern conservation genetics, revealing previously unknown aspects of aquatic mammal behaviour, natural history, population structure and demography. Molecular markers also have been used to define management units, to recognize taxonomic units, to conduct forensic analyses and to control illegal wildlife trade, providing valuable information for decision‐making in wildlife conservation and management.
• 2 We review studies published in peer‐reviewed journals between 1993 and 2010, in which genetic approaches have been applied to conservation‐related issues involving natural populations of 25 species of aquatic mammals in South America. These studies cover just 34% of the 70 aquatic mammal species recorded in South America.
• 3 Most of the studies are related to population structure, phylogeography, gene flow and dispersal movements. In addition, recent findings relate to evolutionarily significant units, management units, forensics and conservation policy.
• 4 Finally, we look to the future and, based on numbers of studies and conservation concerns, suggest which species, geographic areas and genetic studies should be prioritized. Moreover, we discuss constraints on research and suggest collaborative works that would provide critical information towards the effective conservation and management of aquatic mammals in South America.

     

Inclusion of uncertainty in the LCA comparison of different cherry tomato production scenarios

Purpose

Knowledge regarding environmental impacts of agricultural systems is required. Consideration of uncertainty in life cycle assessment (LCA) provides additional scientific information for decision making. The aims of this study were to compare the environmental impacts of different growing cherry tomato cultivation scenarios under Mediterranean conditions and to assess the uncertainty associated to the different agricultural production scenarios.

Materials and methods

The burdens associated to cherry tomato production were calculated and evaluated by the LCA methodology. The functional unit (FU) chosen for this study was the mass unit of 1 t of commercial loose cherry tomatoes. This study included the quantitative uncertainty analysis through Monte Carlo simulation. Three scenarios were considered: greenhouse (GH), screenhouse (SH), and open field (OF). The flows and processes of the product scenario were structured in several sections: structure, auxiliary equipment, fertilizers, crop management, pesticides, and waste management. Six midpoint impact categories were selected for their relevance: climate change, terrestrial acidification, marine eutrophication, metal depletion, and fossil depletion using the impact evaluation method Recipe Midpoint and ecotoxicity using USEtox.

Results and discussion

The structure, auxiliary equipment, and fertilizers produced the largest environmental impacts in cherry tomato production. The greatest impact in these stages was found in the manufacture and drawing of the steel structures, manufacture of perlite, the amount of HDPE plastics used, and the electricity consumed by the irrigation system and the manufacture and application of fertilizers. GH was the cropping scenario with the largest environmental impact in most categories (varying from 18 and 37% higher than SH and OF, respectively, in metal depletion, to 96% higher than SH and OF, in eutrophication). OF showed the highest uncertainty in ecotoxicity, with a bandwidth of 60 CTUe and a probability of 100 and 99.4% to be higher than GH and SH, respectively.

Conclusions

The LCA was used to improve the identification and evaluation of the environmental burdens for cherry tomato production in the Mediterranean area. This study demonstrates the significance of conducting uncertainty analyses for comparative LCAs used in comparative relative product environmental impacts.

     

The molecular phylogeny of the sea star Echinaster (Asteroidea: Echinasteridae) provides insights for genus taxonomy

In this study, we used sequences of two mitochondrial genes, cytochrome c oxidase I (COI) and 16S rRNA, and one nuclear gene, 28S rRNA, to test the monophyly of the sea star genus Echinaster, and understand the phylogenetic relationships among species and subgenera within this genus. Phylogenetic analyses based on Bayesian inference and maximum likelihood methods revealed three clades with high values of genetic divergence among them (K2P distances for COI over 23%). One of the clades grouped all Echinaster (Othilia) species, and the other two clades included Echinaster (non‐Othilia) species and Henricia species, respectively. Although the relationships among Henricia, Othilia, and Echinaster could not be completely clarified, the Othilia clade was a well‐supported group with shared diagnostic morphological characters. Moreover, the approximately unbiased test applied to the phylogenetic reconstruction rejected the hypothesis of the genus Echinaster as a monophyletic group. According to these results, we suggest the revalidation of Othilia as a genus instead of a subgenus within Echinaster. Our study clarifies important points about the phylogenetic relationships among species of Echinaster. Other important systematic questions about the taxonomic classification of Echinaster and Henricia still remain open, but this molecular study provides bases for future research on the topic.     

Comparative study on enzymatic digestibility of switchgrass varieties and harvests processed by leading pretreatment technologies

Feedstock quality of switchgrass for biofuel production depends on many factors such as morphological types, geographic origins, maturity, environmental and cultivation parameters, and storage. We report variability in compositions and enzymatic digestion efficiencies for three cultivars of switchgrass (Alamo, Dacotah and Shawnee), grown and harvested at different locations and seasons. Saccharification yields of switchgrass processed by different pretreatment technologies (AFEX, dilute sulfuric acid, liquid hot water, lime, and soaking in aqueous ammonia) are compared in regards to switchgrass genotypes and harvest seasons. Despite its higher cellulose content per dry mass, Dacotah switchgrass harvested after wintering consistently gave a lower saccharification yield than the other two varieties harvested in the fall. The recalcitrance of upland cultivars and over-wintered switchgrass may require more severe pretreatment conditions. We discuss the key features of different pretreatment technologies and differences in switchgrass cultivars and harvest seasons on hydrolysis performance for the applied pretreatment methods.     

Short and long-term uptake of Hg in white lupin plants:Kinetics and stress indicators

The intrinsic characteristics of white lupin regarding biomass production and tolerance to abiotic stresses could make it a good candidate to be used in degraded mine soils containing mercury (Hg), but white lupin behaviour in response to Hg has to be previously evaluated. With this aim, kinetic parameters of Hg uptake in short and long-term experiments, and Hg resistance of white lupin plants using several stress indicators were studied. The plants were grown with increasing Hg doses in nutrient solutions (0, 5 and 10 μM). Hg uptake showed an active component in Hg influx, suggesting the existence of a low affinity root transporter that can be used for Hg uptake into white lupin root cells. K_m and V_max values obtained for the saturable component were 217.7 ± 27.6 μM and 3.78 ± 0.18 μmol Hg g FW^?1 h^?1. Hg accumulation was concentration–time-dependent, showing a saturable behaviour for the lower doses but a linear behaviour for the highest ones. A high ability of Hg absorption by white lupin was observed both in short and long-term uptake experiments. The highest Hg dose reduced biomass production especially in the shoots. Moreover, increases in chlorophylls, malondialdehyde, total thiols and phenols were observed in Hg-stressed plants. The enhancement of total thiols and phenols levels in roots reduced oxidative stress for the 5 μM dose, but not for higher Hg levels. The deleterious effect of Hg was less marked in root tissues, in spite of their accumulation of very high Hg amounts (99%) because of, at least in part, a combined increase in total thiols and phenolics able to minimize oxidative stress. Our results suggested that phenolic content in roots could be used as a new and easy-to-use indicator of Hg presence. On the whole, white lupin showed a certain ability to survive in Hg-contaminated media and it would be possible to include it in combined decontamination strategies.     

Insulin resistance associated to obesity: the link TNF-alpha

Adipose tissue secretes proteins which may influence insulin sensitivity. Among them, tumour necrosis factor (TNF)-alpha has been proposed as a link between obesity and insulin resistance because TNF-alpha is overexpressed in adipose tissue from obese animals and humans, and obese mice lacking either TNF-alpha or its receptor show protection against developing insulin resistance. The activation of proinflammatory pathways after exposure to TNF-alpha induces a state of insulin resistance in terms of glucose uptake in myocytes and adipocytes that impair insulin signalling at the level of the insulin receptor substrate (IRS) proteins. The mechanism found in brown adipocytes involves Ser phosphorylation of IRS-2 mediated by TNF-alpha activation of MAPKs. The Ser307 residue in IRS-1 has been identified as a site for the inhibitory effects of TNF-alpha in myotubes, with p38 mitogen-activated protein kinase (MAPK) and inhibitor kB kinase being involved in the phosphorylation of this residue. Moreover, up-regulation of protein-tyrosine phosphatase (PTP)1B expression was recently found in cells and animals treated with TNF-alpha. PTP1B acts as a physiological negative regulator of insulin signalling by dephosphorylating the phosphotyrosine residues of the insulin receptor and IRS-1, and PTP1B expression is increased in peripheral tissues from obese and diabetic humans and rodents. Accordingly, down-regulation of PTP1B activity by treatment with pharmacological agonists of nuclear receptors restores insulin sensitivity in the presence of TNF-alpha. Furthermore, mice and cells deficient in PTP1B are protected against insulin resistance induced by this cytokine. In conclusion, the absence or inhibition of PTP1B in insulin-target tissues could confer protection against insulin resistance induced by cytokines.