Differences in the effects of single and mixed species of AMF on the growth and oxidative stress defense in Lolium perenne exposed to hydrocarbons.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous mutualistic plant symbionts that promote plant growth and protect them from abiotic stresses. Studies on AMF-assisted phytoremediation have shown that AMF can increase plant tolerance to the presence of hydrocarbon contaminants by improving plant nutrition status and mitigating oxidative stress. This work aimed to evaluate the impact of single and mixed-species AMF inocula (Funneliformis caledonium, Diversispora varaderana, Claroideoglomus walkeri), obtained from a contaminated environment, on the growth, oxidative stress (DNA oxidation and lipid peroxidation), and activity of antioxidative enzymes (superoxide dismutase, catalase, peroxidase) in Lolium perenne growing on a substrate contaminated with 0/0-30/120 mg phenol/polynuclear aromatic hydrocarbons (PAHs) kg-1. The assessment of AMF tolerance to the presence of contaminants was based on mycorrhizal root colonization, spore production, the level of oxidative stress, and antioxidative activity in AMF spores. In contrast to the mixed-species AMF inoculum, single AMF species significantly enhanced the growth of host plants cultured on the contaminated substrate. The effect of inoculation on the level of oxidative stress and the activity of antioxidative enzymes in plant tissues differed between the AMF species. Changes in the level of oxidative stress and the activity of antioxidative enzymes in AMF spores in response to contamination also depended on AMF species. Although the concentration of phenol and PAHs had a negative effect on the production of AMF spores, low (5/20 mg phenol/PAHs kg-1) and medium (15/60 mg phenol/PAHs kg-1) substrate contamination stimulated the mycorrhizal colonization of roots. Among the studied AMF species, F. caledonium was the most tolerant to phenol and PAHs and showed the highest potential in plant growth promotion. The results presented in this study might contribute to the development of functionally customized AMF-assisted phytoremediation strategies with indigenous AMF, more effective than commercial AMF inocula, as a result of their selection by the presence of contaminants.

Arbuscular mycorrhizal and microbial profiles of an aged phenol-polynuclear aromatic hydrocarbon-contaminated soil.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous, obligatory plant symbionts that have a beneficial influence on plants in contaminated environments. This study focused on evaluating the biomass and biodiversity of the AMF and microbial communities associated with Poa trivialis and Phragmites australis plants sampled at an aged site contaminated with phenol and polynuclear aromatic hydrocarbons (PAHs) and an uncontaminated control site. We analyzed the soil phospholipid fatty acid profile to describe the general structure of microbial communities. PCR-denaturing gradient gel electrophoresis with primers targeting the 18S ribosomal RNA gene was used to characterize the biodiversity of the AMF communities and identify dominant AMF species associated with the host plants in the polluted and control environments. The root mycorrhizal colonization and AMF biomass in the soil were negatively affected by the presence of PAHs and phenol, with no significant differences between the studied plant species, whereas the biodiversity of the AMF communities were influenced by the soil contamination and plant species. Soil contamination was more detrimental to the biodiversity of AMF communities associated with Ph. australis, compared to P. trivialis. Both species favored the development of different AMF species, which might be related to the specific features of their different root systems and soil microbial communities. The contaminated site was dominated by AMF generalists like Funneliformis and Rhizophagus, whereas in the control site Dominikia, Archaeospora, Claroideoglomus, Glomus, and Diversispora were also detected.

Electrochemical treatments of coking wastewater and coal gasification wastewater with Ti/Ti4O7 and Ti/RuO2-IrO2 anodes.

Electrochemical treatments of coking wastewater (CW) and coal gasification wastewater (CGW) were conducted with Ti/Ti4O7 and Ti/RuO2-IrO2 anodes. The performances of Ti/Ti4O7 and Ti/RuO2-IrO2 anodes were investigated by analyzing the effects of five key influencing factors including anodes material, current density, anode-cathode distance, initial pH value, and electrolyte type. The removal efficiencies of total organic carbon (TOC) were analyzed during the processes of CW and CGW electro-oxidation. The removal efficiencies of sixteen polynuclear aromatic hydrocarbons (PAHs) in CW and CGW by electro-oxidation were also explored to further assess the electrochemical activities of Ti/Ti4O7 and Ti/RuO2-IrO2 anodes. The Ti/Ti4O7 anode achieved 78.7% COD removal efficiency of CW, 85.8% COD removal efficiency of CGW, 50.3% TOC removal efficiency of CW, and 54.8% TOC removal efficiency of CGW, higher than the Ti/RuO2-IrO2 anode (76.7%, 78.1%, 44.8% and 46.8%). The COD removal efficiencies increased with the applied current density, decreased with the increase of the anode-cathode distance, and slightly decreased with the increase of the initial pH value. Meanwhile, the removal efficiencies of sixteen PAHs by the Ti/Ti4O7 anode were mostly higher than those by the Ti/RuO2-IrO2 anode. By comprehensively analyzing the performances of Ti/Ti4O7 and Ti/RuO2-IrO2 anodes on electrochemical treatments of CW and CGW, this study may supply insights into the application potentials of these anodes to the electrochemical treatments of real wastewater.

The Molecular Composition of Soot.

Soot (sometimes referred to as black carbon) is produced when hydrocarbon fuels are burned. Our hypothesis is that polynuclear aromatic hydrocarbon (PAH) molecules are the dominant component of soot, with individual PAH molecules forming ordered stacks that agglomerate into primary particles (PP). Here we show that the PAH composition of soot can be exactly determined and spatially resolved by low-fluence laser desorption ionization, coupled with high-resolution mass spectrometry imaging. This analysis revealed that PAHs of 239-838 Da, containing few oxygenated species, comprise the soot observed in an ethylene diffusion flame. As informed by chemical graph theory (CGT), the vast majority of species observed in the sampled particulate matter may be described as benzenoids, consisting of only fused 6-membered rings. Within that limit, there is clear evidence for the presence of radical PAH in the particulate samples. Further, for benzenoid structures the observed empirical formulae limit the observed isomers to those which are nearly circular with high aromatic conjugation lengths for a given aromatic ring count. These results stand in contrast to recent reports that suggest higher aliphatic composition of primary particles.

Presence and Spatial Distribution of Polynuclear Aromatic Hydrocarbons (PAHs) in Groundwater of Merida City, Yucatan, Mexico.

The karstic aquifer of Yucatan features a high permeability, therefore, all contaminants placed in the soil surface, can reach it through infiltration along with the rain water. The purpose of the present study is to determine the spatial distribution of the aromatic hydrocarbons in the underground water of Merida City. Fifty wells inside the city were sampled. The sampling took place during the dry season, from October 2007 to March 2008. Liquid-liquid Hydrocarbon extraction was performed using hexane and purification was made by previously packed chromatography columns. Regarding the occurrence of polynuclear aromatic hydrocarbon (PAHs) traces, 28 water samples (56%) contained residues of these compounds. The following PAHs presented the highest concentrations: benzo(a)anthracene y benzo(k)fluoranthene 13.26 and 7.88 µg L-1 respectively. Only three of the sampled wells showed levels above those allowed by EPA and WHO norms. The origin of these compounds is mainly pyrogenic.

Selective oxidation of alkyl-substituted polyaromatics using ruthenium-ion-catalyzed oxidation.

Ruthenium-ion-catalyzed oxidation of a range of alkylated polyaromatics has been studied. 2-Ethylnaphthalene was used as a model substrate, and oxidation can be performed in either a conventional biphasic or in a monophasic solvent system. In either case the reaction rates and product selectivity are identical. The reaction products indicate that the aromatic ring system is oxidized in preference to the alkyl chain. This analysis is possible due to the development of a quantitative NMR protocol to determine the relative amounts of aliphatic and aromatic protons. From a systematic set of substrates we show that as the length of the alkyl chain substituent on a polyaromatic increases, the proportion of products in which the chain remains attached to the aromatic system increases. Larger polyaromatic systems, based on pyrene and phenanthrene, show greater reactivity than those with fewer aromatic rings, and the alkyl chains are more stable to oxidation.

Biodegradation of creosote-treated wood by two novel constructed microbial consortia for the enhancement of methane production.

Lignocellulose biodegradation is limited because of its recalcitrant structure particularly when polluted by toxic and carcinogenic compounds such as creosote oil (CRO). As far as we know, this might be the first report that explores the biodegradation of creosote treated wood (CTW) to serve biomethane production. Two novel CTW-degrading microbial consortia, designated as CTW-1 and CTW-2, were screened and constructed to enhance methane production from CRO-treated pine sawdust. After 12 days of biological pretreatment by CTW-1 and CTW-2, a significant reduction in lignocellulosic content of CTW was recorded; estimated as 49 and 43%, respectively. More than 64 and 91% of cumulative biogas and methane yields were obtained from biodegraded CTW over control. Ecotoxicity of treated and untreated CTW was compared by Microtox test. The biodegraded CTW hydrolysates showed a toxicity decrease of more than 80%, suggesting the promising role of constructed microbial consortia for biofuel production and bioremediation.

Probabilistic risk assessment for high-end consumers of seafood on the northeastern Gulf coast.

The Deepwater Horizon oil spill (April 20, 2010) caused concern regarding Gulf seafood safety. Communities were skeptical of governmental risk assessments because they did not take into account the higher consumption of seafood along coastal areas. The objective of this study was to perform a probabilistic risk assessment based on the consumption rates of high-end consumers of Gulf seafood. We utilized seafood consumption data from five communities across the northeastern Gulf of Mexico. This study collected finfish, shrimp, blue crab, and oysters from these communities and analyzed their tissues for polynuclear aromatic hydrocarbons (PAHs). A probabilistic risk assessment was performed using population-specific seafood consumption rates and body weights for commercial fishers, recreational fishers, and a Filipino-American community. For non-cancer effects, 95th percentile hazard quotients for these targeted populations ranged between 1.84E-04 to 5.39E-03 for individual seafood types. The 95th percentile hazard indices for total seafood consumption ranged from 3.45E-03 to 8.41E-03. Based on total seafood consumption, highest hazard indices were modeled for the Filipino-American community followed by commercial and recreational fishers. Despite higher consumption rates, hazard indices for the high-end consumers targeted in this study were two to three orders of magnitude below the regulatory limit of 1.

Accuracy and uncertainty analysis of soil Bbf spatial distribution estimation at a coking plant-contaminated site based on normalization geostatistical technologies.

Data distribution is usually skewed severely by the presence of hot spots in contaminated sites. This causes difficulties for accurate geostatistical data transformation. Three types of typical normal distribution transformation methods termed the normal score, Johnson, and Box-Cox transformations were applied to compare the effects of spatial interpolation with normal distribution transformation data of benzo(b)fluoranthene in a large-scale coking plant-contaminated site in north China. Three normal transformation methods decreased the skewness and kurtosis of the benzo(b)fluoranthene, and all the transformed data passed the Kolmogorov-Smirnov test threshold. Cross validation showed that Johnson ordinary kriging has a minimum root-mean-square error of 1.17 and a mean error of 0.19, which was more accurate than the other two models. The area with fewer sampling points and that with high levels of contamination showed the largest prediction standard errors based on the Johnson ordinary kriging prediction map. We introduce an ideal normal transformation method prior to geostatistical estimation for severely skewed data, which enhances the reliability of risk estimation and improves the accuracy for determination of remediation boundaries.

Analysis of polynuclear aromatic hydrocarbons in olive oil after solid-phase extraction using a dual-layer sorbent cartridge followed by high-performance liquid chromatography with fluorescence detection.

A simple and easy direct solid-phase extraction (SPE) method was developed for the analysis of polynuclear aromatic hydrocarbons (PAHs) in olive oil using a dual-layer cartridge containing activated Florisil and a mixture of octadecyl (C18)-bonded and zirconia-coated silicas. Undiluted olive oil was applied directly to the SPE cartridge, and the sample was eluted with acetonitrile solvent. Background in the extract was found to be low enough for either gas chromatography-mass spectrometry (GC-MS) or high-performance liquid chromatography with fluorescence detection (HPLC-FLD) analysis. Average recoveries for 16 different PAHs from spiked olive oil replicates were >75%, with intraday precisions of <20% relative standard deviation (% RSD). Detection limits ranged from 0.2 to 1.0 µg/kg and, specifically for the PAHs listed in EC Regulation 835/2011, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, and benzo(a)pyrene, were from 0.3 to 0.7 µg/kg. The method was then applied to determine the PAH content present in commercial samples of refined versus extra-virgin olive oils.

The phn Island: A New Genomic Island Encoding Catabolism of Polynuclear Aromatic Hydrocarbons.

Bacteria are key in the biodegradation of polycyclic aromatic hydrocarbons (PAH), which are widespread environmental pollutants. At least six genotypes of PAH degraders are distinguishable via phylogenies of the ring-hydroxylating dioxygenase (RHD) that initiates bacterial PAH metabolism. A given RHD genotype can be possessed by a variety of bacterial genera, suggesting horizontal gene transfer (HGT) is an important process for dissemination of PAH-degrading genes. But, mechanisms of HGT for most RHD genotypes are unknown. Here, we report in silico and functional analyses of the phenanthrene-degrading bacterium Delftia sp. Cs1-4, a representative of the phn(AFK2) RHD group. The phn(AFK2) genotype predominates PAH degrader communities in some soils and sediments, but, until now, their genomic biology has not been explored. In the present study, genes for the entire phenanthrene catabolic pathway were discovered on a novel ca. 232 kb genomic island (GEI), now termed the phn island. This GEI had characteristics of an integrative and conjugative element with a mobilization/stabilization system similar to that of SXT/R391-type GEI. But, it could not be grouped with any known GEI, and was the first member of a new GEI class. The island also carried genes predicted to encode: synthesis of quorum sensing signal molecules, fatty acid/polyhydroxyalkanoate biosynthesis, a type IV secretory system, a PRTRC system, DNA mobilization functions and >50 hypothetical proteins. The 50% G + C content of the phn gene cluster differed significantly from the 66.7% G + C level of the island as a whole and the strain Cs1-4 chromosome, indicating a divergent phylogenetic origin for the phn genes. Collectively, these studies added new insights into the genetic elements affecting the PAH biodegradation capacity of microbial communities specifically, and the potential vehicles of HGT in general.

Development of Tools for Genetic Analysis of Phenanthrene Degradation and Nanopod Production by Delftia sp. Cs1-4.

The bacterium Delftia sp. Cs1-4 produces novel extracellular structures (nanopods) in conjunction with its growth on phenanthrene. While a full genome sequence is available for strain Cs1-4, genetic tools that could be applied to study phenanthrene degradation/nanopod production have not been reported. Thus, the objectives of this study were to establish such tools, and apply them for molecular analysis of nanopod formation or phenanthrene degradation. Three types of tools were developed or validated. First, we developed a new expression system based on a strong promoter controlling expression of a surface layer protein (NpdA) from Delftia sp. Cs1-4, which was ca. 2,500-fold stronger than the widely used lactose promoter. Second, the Cre-loxP system was validated for generation of markerless, in-frame, gene deletions, and for in-frame gene insertions. The gene deletion function was applied to examine potential roles in nanopod formation of three genes (omp32, lasI, and hcp), while the gene insertion function was used for reporter gene tagging of npdA. Lastly, pMiniHimar was modified to enhance gene recovery and mutant analysis in genome-wide transposon mutagenesis. Application of the latter to strain Cs1-4, revealed several new genes with potential roles in phenanthrene degradation or npdA expression. Collectively, the availability of these tools has opened new avenues of investigation in Delftia sp. Cs1-4 and other related genera/species with importance in environmental toxicology.