Investigation of obesogenic effects of hexachlorobenzene, DDT and DDE in male rats.

Obesity has become a very important public health problem and is increasing globally. Genetics, individual and environmental factors play roles in the etiology of this complex disorder. Recently, several environmental pollutants have been suggested to have obesogenic activities. Peroxisome proliferator activating receptor gamma (PPARγ), uncoupling protein-1 (UCP1) and their expression in white adipose tissue (WAT) and brown adipose tissue (BAT) play key roles in adipogenesis. UCP3 and irisin were reported to play roles in non-shivering thermogenesis. Our primary aim was to investigate obesogenic effects of hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) in rats. In addition, thermoregulatory effects of HCB, DDT and DDE were also investigated by analyzing the levels of Ucp3 and irisin. Thirty-two adult male Sprague-Dawley rats were randomly divided into four groups as control, HCB, DDT and DDE. Animals were administered with organochlorine pesticides (OCPs; 5 mg/kg bw) by oral gavage every other day for five weeks. At the end of the experimental period, the animals were sacrificed, BAT and WAT samples were collected to analyze Pparγ, Ucp1 and Ucp3 levels. Moreover, skeletal muscle samples were collected to examine Ucp3 and irisin levels. Serum glucose, cholesterol and triglyceride levels were also determined. Body weight and core temperature of the animals were not significantly affected by any of the OCP administration. Serum glucose, cholesterol and triglyceride levels were similar among the experimental groups. Pparγ expression was significantly elevated by HCB administration only in WAT (p < 0.05). On the other hand, both Pparγ and Ucp1 expressions were diminished in WAT and BAT (p < 0.01) by DDT treatment, while in WAT, DDE significantly decreased Pparγ expression without altering its expression in BAT (p < 0.001). Ucp3 and irisin levels in skeletal muscle were not altered. Our findings show that both DDT and DDE reduce the browning of WAT by suppressing white adipocytes and thus may have obesogenic activity in male rats without altering thermoregulation. In addition, HCB, DDT and DDE-induced alterations in expression of Pparγ and Ucp1 in WAT implicates differential regulation of adipogenic processes.

Manganese mitigates against hepatorenal oxidative stress, inflammation and caspase-3 activation in rats exposed to hexachlorobenzene.

The present study investigated the individual and collective effect of organochlorinated fungicide hexachlorobenzene (HCB) and manganese (Mn), a metal, on the hepatorenal function in adult rats. Rats were divided into four groups of rats comprising of control, HCB alone (15 mg/kg), Mn alone (10 mg/kg) and co-exposure group that were orally treated for 25 consecutive days. After sacrifice, hepatorenal damage and antioxidant status markers, myeloperoxidase (MPO) activity, levels of nitric oxide, total antioxidant capacity (TAC), total oxidative stress (TOS) and lipid peroxidation (LPO) were analyzed spectrophotometrically. Levels of tumor necrosis factor alpha (TNF-α), interleukin-1 ß (IL-1ß) and caspase-3 activity were assessed using ELISA. Results revealed that the HCB administration significantly (p < 0.05) increased the biomarkers of hepatorenal toxicity, decreased the antioxidant status and TAC, raised the levels of TOS and LPO as well as increased the levels of TNF-α, IL-1ß and caspase-3 activity. Rats co-exposed to HCB and Mn showed decreased biomarkers of hepatorenal damage, increased antioxidant status and TAC with simultaneous reduction in the levels of TOS and LPO significantly (p < 0.05). Furthermore, the increased levels of TNF-α, IL-1ß and caspase-3 activity were significantly (p < 0.05) reduced in the liver and kidney of rats' co-expose to HCB and Mn. Histological examination showed that damages induced by HCB were assuaged in rats co-treated with HCB and Mn. In conclusion, the results demonstrated that co-treatment of HCB and Mn in rats' alleviated HCB-induced oxidative stress, inflammation and caspase-3 activation in the liver and kidney of the rats.

Hexachlorobenzene Monooxygenase Substrate Selectivity and Catalysis: Structural and Biochemical Insights.

Hexachlorobenzene (HCB), as one of the persistent organic pollutants (POPs) and a possible human carcinogen, is especially resistant to biodegradation. In this study, HcbA1A3, a distinct flavin-N5-peroxide-utilizing enzyme and the sole known naturally occurring aerobic HCB dechlorinase, was biochemically characterized. Its apparent preference for HCB in binding affinity revealed that HcbA1 could oxidize only HCB rather than less-chlorinated benzenes such as pentachlorobenzene and tetrachlorobenzenes. In addition, the crystal structure of HcbA1 and its complex with flavin mononucleotide (FMN) were resolved, revealing HcbA1 to be a new member of the bacterial luciferase-like family. A much smaller substrate-binding pocket of HcbA1 than is seen with its close homologues suggests a requirement of limited space for catalysis. In the active center, Tyr362 and Asp315 are necessary in maintaining the normal conformation of HcbA1, while Arg311, Arg314, Phe10, Val59, and Met12 are pivotal for the substrate affinity. They are supposed to place HCB at a productive orientation through multiple interactions. His17, with its close contact with the site of oxidation of HCB, probably fixes the target chlorine atom and stabilizes reaction intermediates. The enzymatic characteristics and crystal structures reported here provide new insights into the substrate specificity and catalytic mechanism of HcbA1, which paves the way for its rational engineering and application in the bioremediation of HCB-polluted environments.IMPORTANCE As an endocrine disrupter and possible carcinogen to human beings, hexachlorobenzene (HCB) is especially resistant to biodegradation, largely due to difficulty in its dechlorination. The lack of knowledge of HCB dechlorinases limits their application in bioremediation. Recently, an HCB monooxygenase, HcbA1A3, representing the only naturally occurring aerobic HCB dechlorinase known so far, was reported. Here, we report its biochemical and structural characterization, providing new insights into its substrate selectivity and catalytic mechanism. This research also increases our understanding of HCB dechlorinases and flavin-N5-peroxide-utilizing enzymes.

Angiogenesis signaling in breast cancer models is induced by hexachlorobenzene and chlorpyrifos, pesticide ligands of the aryl hydrocarbon receptor.

Breast cancer incidence is increasing globally and pesticides exposure may impact risk of developing this disease. Hexachlorobenzene (HCB) and chlorpyrifos (CPF) act as endocrine disruptors, inducing proliferation in breast cancer cells. Vascular endothelial growth factor-A (VEGF-A), cyclooxygenase-2 (COX-2) and nitric oxide (NO) are associated with angiogenesis. Our aim was to evaluate HCB and CPF action, both weak aryl hydrocarbon receptor (AhR) ligands, on angiogenesis in breast cancer models. We used: (1) in vivo xenograft model with MCF-7 cells, (2) in vitro breast cancer model with MCF-7, and (3) in vitro neovasculogenesis model with endothelial cells exposed to conditioned medium from MCF-7. Results show that HCB (3 mg/kg) and CPF (0.1 mg/kg) stimulated vascular density in the in vivo model. HCB and CPF low doses enhanced VEGF-A and COX-2 expression, accompanied by increased levels of nitric oxide synthases (NOS), and NO release in MCF-7. HCB and CPF high doses intensified VEGF-A and COX-2 levels but rendered different effects on NOS, however, both pesticides reduced NO production. Moreover, our data indicate that HCB and CPF-induced VEGF-A expression is mediated by estrogen receptor and NO, while the increase in COX-2 is through AhR and NO pathways in MCF-7. In conclusion, we demonstrate that HCB and CPF environmental concentrations stimulate angiogenic switch in vivo. Besides, pesticides induce VEGF-A and COX-2 expression, as well as NO production in MCF-7, promoting tubulogenesis in endothelial cells. These findings show that pesticide exposure could stimulate angiogenesis, a process that has been demonstrated to contribute to breast cancer progression.

Hexachlorobenzene Catabolism Involves a Nucleophilic Aromatic Substitution and Flavin-N5-Oxide Formation.

HcbA1 is a unique flavoenzyme that catalyzes the first step in the bacterial hexachlorobenzene catabolic pathway. Here we report in vitro reconstitution of the HcbA1-catalyzed reaction. Detailed mechanistic studies provide evidence for nucleophilic aromatic substitution and flavin-N5-oxide formation.

Excretion kinetics of three dominant organochlorine compounds in human milk within the first 6 months postpartum.

Breastfeeding is a specific and important way for women to eliminate harmful substances accumulated in body. Hexachlorobenzene (HCB), ß-hexachlorocyclohexane (ß-HCH), and 2,2-bis(p-chlorophenyl)-1,1-dichloroethene (p,p'-DDE) are dominant organochlorine compounds(OCCs) and persistent organic pollutants (POPs) accumulated in human being. Although a 6-month breastfeeding was suggested by the World Health Organization (WHO), the excretion characteristics of OCCs in human milk during the first 6-month lactation remain controversial. The main purpose of this study was to continuously monitor the three dominant OCC concentrations and reveal their elimination characteristic in human milk within the first 6-month lactation. To do that, with one sample per month, during their first 6-month lactation, human milk samples were continuously collected from 40 mothers after their first birth. The result showed that the concentrations of the three OCCs in human milk during the lactation continuously decreased from 51.7 to 39.9 µg/kg milk lipids for HCB, from 136.5 to 84.8 µg/kg milk lipids for ß-HCH, and from 307.3 to 192 µg/kg milk lipids, respectively. The excretion kinetics of each compound in milk lipids fitted zero-order kinetics during the 6-month lactation. The excretion rate of the three OCCs was approximately 3% per month for HCB and 7% per month for the other two compounds during the lactation, with tdec 1/2 of 13 months for HCB, 7.5 months for ß-HCH, and 8 months for p,p'-DDE. The excretion rate of the target compounds depended on initial deposited levels, compound properties, and exposure or input source.

An approach to biodegradation of chlorobenzenes: combination of Typha angustifolia and bacterial effects on hexachlorobenzene degradation in water.

Although rhizoremediation is an effective approach to remove organic pollutants from the environment, little is known about the mechanism of hexachlorobenzene (HCB) biodegradation in water. In this study, we used Typha angustifolia (T. angustifolia) grown in sterile Hoagland nutrient solution to determine the rhizosphere effects on the ability of bacteria in water to reduce HCB levels. The results revealed that T. angustifolia could facilitate HCB degradation and that the initial HCB concentration was the major factor responsible for HCB degradation in nutrient solution. Furthermore, HCB biodegradation in low-HCB nutrient solution with T. angustifolia fitted the first-order kinetics, owing to the high concentration of total organic carbon, low HCB toxicity, and unique bacterial community in the T. angustifolia rhizosphere. Denaturing gradient gel electrophoresis indicated that the rhizosphere effects and different dosages of HCB have significant effects on the bacterial communities by repressing and favoring certain populations. The most successful bacteria to adapt to HCB contamination was Bacillus sp., while the dominant bacterial phyla in HCB-polluted water were Proteobacteria and Firmicutes.

Calibration of a plant uptake model with plant- and site-specific data for uptake of chlorinated organic compounds into radish.

The uptake of organic pollutants by plants is an important process for the exposure of humans to toxic chemicals. The objective of this study was to calibrate the parameters of a common plant uptake model by comparison to experimental results from literature. Radish was grown in contaminated soil (maximum concentration 2.9 mg/kg dw) and control plot. Uptake of HCHs, HCB, PCBs, and DDT plus metabolites was studied (log K(ow) 3.66 to 7.18). Measured BCF roots-to-soil were near 1 g/g dw on the control plot and about factor 10 lower for the contaminated soil. With default data set, uptake into roots of most substances was under predicted up to factor 100. The use of site-specific data improved the predictions. Consideration of uptake from air into radish bulbs was relevant for PCBs. Measured BCF shoots ranged from <0.1 to >10 g/g dw and were much better predicted by the standard model. The results with default data and site-specific data were similar. Deposition from air was the major uptake mechanism into shoots. Transport from soil with resuspended particles was only relevant for the contaminated plot. The calculation results (in dry weight) were most sensitive to changes of the water content of plant tissue.

Biodegradation of hexachlorobenzene by a constructed microbial consortium.

A consortium comprised of an engineered Escherichia coli DH5α and a natural pentachlorophenol (PCP) degrader, Sphingobium chlorophenolicum ATCC 39723, was assembled for degradation of hexachlorobenzene (HCB), a persistent organic pollutant. The engineered E. coli strain, harbouring a gene cassette (camA (+) camB (+) camC) that encodes the F87W/Y96F/L244A/V247L mutant of cytochrome P-450cam (CYP101), oxidised HCB to PCP. The resulting PCP was then further completely degraded by ATCC 39723. The results showed that almost 40 % of 4 µM HCB was degraded by the consortium at a rate of 0.033 nmol/mg (dry weight)/h over 24 h, accompanied by transient accumulation and immediate consumption of the intermediate PCP, detected by gas chromatography. In contrast, in the consortium comprised of Pseudomonas putida PaW340 harbouring camA (+) camB (+) camC and ATCC 39723, PCP accumulated in PaW340 cells but could not be further degraded, which may be due to a permeability barrier of Pseudomonas PaW340 for PCP transportation. The strategy of bacterial co-culture may provide an alternative approach for the bioremediation of HCB contamination.

Limited reversibility of bioconcentration of hydrophobic organic chemicals in phytoplankton.

Aging, reversibility, and desorption rates for the binding of hydrophobic chemicals (HOC) to phytoplankton cells have not been directly measured. Here the effect of bioconcentration time on subsequent desorption of hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) was studied for the alga Monoraphidium minutum. Cell suspensions were exposed to HCB and PCBs spanning a range of log Kow values of 5.7 to 8.2, for 0.13 to 14 d. Subsequently, reversibility and desorption rates were assessed by extracting the chemicals from the cells using infinite sink extractions with Tenax beads or Empore disks employed in the cell suspension. Uptake was biphasic with constant relative contributions of fast surface sorption. Desorption was biphasic too and well fitted to a first order two compartment model. Increasing exposure times resulted in increasing slowly desorbing chemical fractions and decreased desorption rates from these fractions. For the most hydrophobic PCBs, slowly desorbing fractions were >80-90%, whereas desorption half-lives from these fractions ranged up to 120 days. The slow desorption rates directly prove that bioconcentration to algae can be rate limited and imply that already after a few hours of exposure, HOCs may become practically unavailable for repartitioning.

Comparison of targeted peptide quantification assays for reductive dehalogenases by selective reaction monitoring (SRM) and precursor reaction monitoring (PRM).

Targeted absolute protein quantification yields valuable information about physiological adaptation of organisms and is thereby of high interest. Especially for this purpose, two proteomic mass spectrometry-based techniques namely selective reaction monitoring (SRM) and precursor reaction monitoring (PRM) are commonly applied. The objective of this study was to establish an optimal quantification assay for proteins with the focus on those involved in housekeeping functions and putative reductive dehalogenase proteins from the strictly anaerobic bacterium Dehalococcoides mccartyi strain CBDB1. This microbe is small and slow-growing; hence, it provides little biomass for comprehensive proteomic analysis. We therefore compared SRM and PRM techniques. Eleven peptides were successfully quantified by both methods. In addition, six peptides were solely quantified by SRM and four by PRM, respectively. Peptides were spiked into a background of Escherichia coli lysate and the majority of peptides were quantifiable down to 500 amol absolute on column by both methods. Peptide quantification in CBDB1 lysate resulted in the detection of 15 peptides using SRM and 14 peptides with the PRM assay. Resulting quantification of five dehalogenases revealed copy numbers of <10 to 115 protein molecules per cell indicating clear differences in abundance of RdhA proteins during growth on hexachlorobenzene. Our results indicated that both methods show comparable sensitivity and that the combination of the mass spectrometry assays resulted in higher peptide coverage and thus more reliable protein quantification.

Varying temporal trends in the levels of six groups of legacy persistent organic pollutants (POPs) in liver of three gadoid species from the North Sea.

From 2005 to 2019, three gadoid species, Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and saithe (Pollachius virens), were sampled approximately every third year in the northeastern part of the North Sea. Liver samples were analyzed to investigate levels and temporal trends of six groups of persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its degradation products, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), trans-nonachlor (TNC), and polybrominated diphenyl ethers (PBDEs). Some of the highest average concentrations were found in cod, the levels otherwise being similar between the three species and mostly below established threshold values. The levels of all the contaminants except HCB and TNC were higher than previously reported for cod and haddock in the Barents Sea. Significantly decreasing levels were found for Σ7PCBs, ΣDDTs, ΣHCHs and Σ15PBDEs in all three species, and for TNC in haddock and saithe, while there was no significant trend for TNC in cod. HCB levels increased significantly in cod and haddock and showed only a minor decrease in saithe. The observed time trends of legacy POPs demonstrate the persistence of some of the studied pollutants despite efforts to eliminate them from the marine environment.

Triple negative breast cancer cells exposed to aryl hydrocarbon receptor ligands hexachlorobenzene and chlorpyrifos activate endothelial cells.

Breast cancer is currently one of the most prevalent cancers worldwide. The mechanisms by which pesticides can increase breast cancer risk are multiple and complex. We have previously observed that two aryl hydrocarbon receptor (AhR) agonists ‒pesticides hexachlorobenzene (HCB) and chlorpyrifos (CPF)‒ act on tumor progression, stimulating cell migration and invasion in vitro and tumor growth in animal models. Elevated levels of hypoxia inducible factor-1α (HIF-1α) are found in malignant breast tumors, and HIF-1α is known to induce proangiogenic factors such as vascular endothelial growth factor (VEGF), nitric oxide synthase-2 (NOS-2) and cyclooxygenase-2 (COX-2), which are fundamental in breast cancer progression. In this work, we studied HCB (0.005, 0.05, 0.5 and 5 µM) and CPF (0.05, 0.5, 5 and 50 µM) action on the expression of these proangiogenic factors in triple negative breast cancer cells MDA-MB-231, as well as the effect of their conditioned medium (CM) on endothelial cells. Exposure to pesticides increased HIF-1α and VEGF protein expression in an AhR-dependent manner. In addition, HCB and CPF boosted NOS-2 and COX-2 content and VEGF secretion in MDA-MB-231 cells. The treatment of endothelial cells with CM from tumor cells exposed to pesticides increased cell proliferation, migration, and tubule formation, enhancing both tubule length and branching points. Of note, these effects were VEGF-dependent, as they were blocked in the presence of a VEGF receptor-2 (VEGFR-2) inhibitor. In sum, our results highlight the harmful impact of HCB and CPF in modulating the interaction between breast cancer and endothelial cells and promoting angiogenesis.

The "degradative" and "biological" pumps controls on the atmospheric deposition and sequestration of hexachlorocyclohexanes and hexachlorobenzene in the North Atlantic and Arctic Oceans.

The cycling of hexachlorobenzene (HCB) and hexachlorocyclohexanes (HCHs) has been studied in the North Atlantic and Arctic Ocean. Concentrations of HCHs and HCB were measured simultaneously in the atmosphere (gas and aerosol phases), seawater (dissolved and particulate phases), and phytoplankton. The atmospheric concentrations of HCHs decrease during transport over the Greenland Current with estimated e-folding times of 1.6 days, a trend not observed for HCB. This strong decrease in atmospheric concentrations of HCH is consistent with the estimated atmospheric depositional fluxes driven by the air-water disequilibrium. The removal of HCHs from the surface ocean by the degradative pump due to hydrolysis and microbial degradation and by the biological pump due to settling of particle-associated HCHs are estimated; the removal fluxes are within a factor of 2 of the atmospheric inputs for most sampling events, suggesting an important role of the degradative pump in the overall oceanic sink of HCHs. Conversely, the lack of degradation of HCB in surface waters and its relatively low hydrophobicity imply a lack of effective removal processes, consistent with the observed air and water concentrations close to equilibrium. This work is the first that estimates the relative importance of the biological and degradative pumps on the atmospheric deposition of the less persistent organic pollutants and points out the need for further research for quantifying the magnitude of degradative processes in the environment.

Enrichment of hexachlorobenzene and 1,3,5-trichlorobenzene transforming bacteria from sediments in Germany and Vietnam.

Bacterial cultures were enriched from sediments in Germany and Vietnam reductively dechlorinating hexachlorobenzene and the highly persistent 1,3,5-trichlorobenzene to monochlorobenzene. The main products of the reductive dechlorination of hexachlorobenzene were monochlorobenzene and dichlorobenzenes (1,2-; 1,3- and 1,4-dichlorobenzene) while no trichlorobenzenes accumulated. For the reductive dechlorination of 1,3,5-trichlorobenzene with the mixed culture from Vietnam sediment, 1,3- dichlorobenzene and monochlorobenzene were produced as intermediate and final end-product, respectively. The pattern of dechlorination did not change when the cultures were repeatedly exposed to oxygen over seven transfers demonstrating oxygen tolerance of the dechlorinating bacteria. However, reductive dechlorination of 1,3,5-trichlorobenzene was inhibited by vancomycin at a concentration of 5 mg L(-1). Vancomycin delayed reductive dechlorination of hexachlorobenzene in mixed cultures by about 6 months. When repeatedly applied, vancomycin completely abolished the ability of the mixed culture to transform hexachlorobenzene. Sensitivity to vancomycin and insensitivity to brief exposure of oxygen indicates that the dechlorinating bacteria in the mixed cultures did not belong to the genus Dehalococcoides.

Bioaccumulation of HCH isomers in selected macroinvertebrates from the Elbe River: sources and environmental implications.

Sediments of the Elbe River have been extremely polluted by contaminants originating from previous large-scale hexachlorocyclohexane (HCH) production and the application of γ-HCH (lindane) in its catchment in the second half of the twentieth century. In order to gain knowledge on bioaccumulation processes at lower trophic levels, field investigations of HCHs in macroinvertebrates were carried out along the longitudinal profile of the Elbe and tributary. Among the sites studied, concentrations in macroinvertebrates ranged within five orders of magnitude (0.01-100 µg/kg). In general, lower values of HCH isomers were observed at all Czech sites (mostly <1 µg/kg) compared with those in Germany. At the most contaminated site, Spittelwasser brook (a tributary of the Mulde), extremely high concentrations were measured (up to 234 µg/kg α-HCH and 587 µg/kg ß-HCH in Hydropsychidae). In contrast, the Obríství site, though also influenced by HCH production facilities, showed only negligibly elevated values (mostly <1 µg/kg). Results showed that fairly high levels of α-HCH and ß-HCH compared to γ-HCH can still be detected in aquatic environments of the Elbe catchment, and these concentrations are decreasing over time to a lesser extent than γ-HCH. Higher HCH concentrations in sediments in the springtime are considered to be the result of erosion and transport processes during and after spring floods, and lower concentrations at sites downstream are thought to be caused by the time lapse involved in the transportation of contaminated particles from upstream. In addition, comparison with fish (bream) data from the literature revealed no increase in tissue concentrations between invertebrates and fish.

Occurrence of higher chlorinated benzenes in livers of grass carp and common carp collected from markets of Xinxiang, China.

Five higher chlorinated benzenes (including hexachlorobenzene (HCB), pentachlorobenzene (PeCB) and three isomers of tetrachlorobenzens) were measured in the livers of grass carp and common carp collected from five markets in Xinxiang city, China. HCB and PeCB were detected in all samples. The major component of the higher CBs residue was HCB and significant correlations existed between HCB and PeCB in both grass carp and common carp livers. The ratio range of HCB/PeCB in grass carp and common carp were 3.4-6.2 and 4.9-7.7, respectively, which implied the sources of higher CBs originate mainly from the revolatilization of industrial HCB with a minor impact from PeCB.

Fe2O3 micron particles are critical for electron transfer and the distribution of electrochemically active bacteria in soil MFCs.

Fe2O3 plays a complex role in soil electron transfer. A microbial fuel cell (MFC) was constructed to drive the directional transfer of electrons in soil, and the results revealed that Fe2O3 acts first as a capacitor, intercepting and reserving the electrons produced by electrochemically active bacteria (EAB) in the soil, which leads to a decrease in hexachlorobenzene (HCB) removal efficiency with increasing proportions of Fe2O3 dosing (R2 = 0.85). The Fe2O3 then exerted its semiconductor properties in synergy with dissolved Fe2+ as an electron mediator to promote the flow of electrons in the soil. Power generation by the MFC was significantly and positively correlated with the concentration of dissolved Fe2+ (r = 0.51) and the Fe2O3 dosing proportion (r = 0.97). The higher HCB removal efficiency, spatial distribution of intercepted electrons, and abundance of electron transfer metabolic pathways confirmed that Fe2O3 promoted electron-flow fluxes in soil. Additionally, Geobacter sp., (direct electron transfer) and Pseudomonas sp., (indirect electron transfer) were the dominant electrochemically active bacteria in the anode and soil of MFC, respectively. In this study, both dissolved (Fe2+) and solid state (Fe2O3) electron mediators functioned as electron transporters in soil, we propose an internal "electron internet" of soil consisting of points and lines.

The deep dive of organohalogen compounds: Bioaccumulation in the top predators of mesopelagic trophic webs, pygmy and dwarf sperm whales, from the Southwestern Atlantic ocean.

Kogia sima and Kogia breviceps are apex predators of mesopelagic trophic webs being far from most anthropogenic threats. However, chemical pollutants and naturally synthesized compounds may travel long distances. This study aimed to use kogiid whales as sentinels of mesopelagic trophic webs in the Southwestern Atlantic Ocean. Persistent organic pollutants (POPs), e.g., polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and metabolites, mirex, hexachlorobenzene (HCB), polybrominated diphenylethers (PBDEs), pentabromoethylbenzene (PBEB) and hexabromobenzene (HBB), and the naturally produced methoxylated BDE (MeO-BDEs) were determined in the blubber of 16 K. sima and 15 K. breviceps. Among the organochlorine compounds, DDTs were the main group found in K. sima and in K. breviceps (1636.6 and 3983.3 ng g-1 lw, respective medians), followed by PCBs (425.9 and 956.1 ng g-1 lw, respectively), mirex (184.1 and 375.6 ng g-1 lw, respectively), and HCB (132.4 and 340.3 ng g-1 lw, respectively). As for the organobromine, the natural MeO-BDEs were predominant (1676.7 and 501.6 ng g-1 lw, respectively), followed by PBDEs (13.6 and 10.3 ng g-1 lw, respectively) and PBEB (2.2 and 2.9 ng g-1 lw, respectively). In general, POPs concentration was higher in K. breviceps than in K. sima. Conversely, MeO-BDEs concentration was higher in K. sima than in K. breviceps. Differences in concentrations in these sympatric odontocetes were attributed to distinct species, sampling sites, and biological parameters and suggest some level of niche segregation. It is noteworthy the long-range reach and bioaccumulation of these synthetic compounds in an unexplored habitat, that present an increasing economic interest.

Hydration state of the moss Hylocomium splendens and the lichen Cladina stellaris governs uptake and revolatilization of airborne α- and γ-hexachlorocyclohexane.

The partitioning of α- and γ-hexachlorocyclohexane between air and the moss Hylocomium splendens and the lichen Cladina stellaris were studied under laboratory conditions. After cultivation of the sample material to obtain a common starting point free from outside influence, the material was divided into four different treatment categories with different hydration/desiccation regimes. The concentrations of the analytes were 3-5 times higher in the hydrated moss or lichen than in the desiccated material. The results are in contrast to how these compounds are taken up by pine needles in which there is a continuous accumulation, more rapid during periods with high temperatures and dry weather. In general, the different adaptations to water economy is a more important explanatory factor for the concentration of airborne hydrophobic pollutants in mosses, lichens, and vascular plants than their designation as "plants" in a broad sense. It is, therefore, not advisible to mix data from different organism groups for monitoring or modeling purposes.