Heterogeneous Antibiotic Resistance Gene Removal Impedes Evaluation of Constructed Wetlands for Effective Greywater Treatment.

Microorganisms carrying antimicrobial resistance genes are often found in greywater. As the reuse of greywater becomes increasingly needed, it is imperative to determine how greywater treatment impacts antimicrobial resistance genes (ARGs). Using qPCR and SmartChip™ qPCR, we characterized ARG patterns in greywater microbial communities before, during, and after treatment by a recirculating vertical flow constructed wetland. In parallel, we examined the impact of greywater-treated irrigation on soil, including the occurrence of emerging micropollutants and the taxonomic and ARG compositions of microbial communities. Most ARGs in raw greywater are removed efficiently during the winter season, while some ARGs in the effluents increase in summer. SmartChip™ qPCR revealed the presence of ARGs, such as tetracycline and beta-lactam resistance genes, in both raw and treated greywater, but most abundantly in the filter bed. It also showed that aminoglycoside and vancomycin gene abundances significantly increased after treatment. In the irrigated soil, the type of water (potable or treated greywater) had no specific impact on the total bacterial abundance (16S rRNA gene). No overlapping ARGs were found between treated greywater and greywater-irrigated soil. This study indicates ARG abundance and richness increased after treatment, possibly due to the concentration effects of the filter beds.

Biotransformation of 2,4,6-trinitrotoluene by Diaphorobacter sp. strain DS2.

Diaphorobacter strain DS2 degrades 3-nitrotoluene and 2-nitrotoluene via ring oxidation with 3-nitrotoluene dioxygenase (3NTDO). In the current study, we hypothesized that 3NTDO might also be involved in the degradation of 2,4,6-trinitrotoluene (TNT), a major nitroaromatic explosive contaminant in soil and groundwater. Strain DS2 transforms TNT as a sole carbon and nitrogen source when grown on it. Ammonium chloride and succinate in the medium accelerated the TNT degradation rate. A resting cell experiment suggested that TNT does not compete with 3NT degradation (no negative impact of TNT on the reaction velocity for 3NT). Enzyme assay with 3NTDO did not exhibit TNT transformation activity. The above results confirmed that 3NTDO of DS2 is not responsible for TNT degradation. In the resting cell experiment, within 10 h, 4ADNT completely degraded. The degradation of 2ADNT was 97% at the same time. We hypothesized that 3NTDO involve in this reaction. Based on the DS2 genome, we proposed that the N-ethylmaleimide reductases (nemA) were involved in the initial reduction of the nitro group and aromatic ring of TNT. Our findings suggest that strain DS2 could be helpful for the removal of TNT from contaminated sites with or without any additional carbon and nitrogen source and with minimal accumulation of undesirable intermediates.

Oxyanion Removal from Impaired Water by Donnan Dialysis Plug Flow Contactors.

In the last twenty-five years, extensive work has been done on ion exchange membrane bioreactors (IEMB) combining Donnan dialysis and anaerobic reduction to remove trace oxyanions (e.g., perchlorate, nitrate, chlorate, arsenate) from contaminated water sources. Most studies used Donnan dialysis contactors with high recirculation rates on the feed side, so under continuous operation, the effective concentration on the feed side of the membrane is the same as the exit concentration (CSTR mode). We have built, characterized, and modelled a plug flow Donnan dialysis contactor (PFR) that maximizes concentration on the feed side and operated it on feed solutions spiked with perchlorate and nitrate ion using ACS and PCA-100 anion exchange membranes. At identical feed inlet concentrations with the ACS membrane, membrane area loading rates are three-fold greater, and fluxes are more than double in the PFR contactor than in the CSTR contactor. A model based on the nonlinear adsorption of perchlorate in ACS membrane correctly predicted the trace ion concentration as a function of space-time in experiments with ACS. For PCA membrane, a linear flux dependence on feed concentration correctly described trace ion feed concentration as a function of space-time. Anion permeability for PCA-100 was high enough that the overall mass transfer was affected by the film boundary layer resistance. These results provide a basis for efficiently scaling up Donnan dialysis contactors and incorporating them in full-scale IEMB setups.

Mitigation of antimicrobial resistance genes in greywater treated at household level.

Greywater often contains microorganisms carrying antimicrobial resistance genes (ARGs). Reuse of greywater thus potentially facilitates the enrichment and spread of multidrug resistance, posing a possible hazard for communities that use it. As water reuse becomes increasingly necessary, it is imperative to determine how greywater treatment impacts ARGs. In this study, we characterize ARG patterns in greywater microbial communities before and after treatment by a recirculating vertical flow constructed wetland (RVFCW). This greywater recycling method has been adopted by some small communities and households for greywater treatment; however, its ability to remove ARGs is unknown. We examined the taxonomic and ARG compositions of microbial communities in raw and treated greywater from five households using shotgun metagenomic sequencing. Total ARGs decreased in abundance and diversity in greywater treated by the RVFCW. In parallel, the microbial communities decreased in similarity in treated greywater. Potentially pathogenic bacteria associated with antimicrobial resistance and mobile genetic elements were detected in both raw and treated water, with a decreasing trend after treatment. This study indicates that RVFCW systems have the potential to mitigate antimicrobial resistance-related hazards when reusing treated greywater, but further measures need to be taken regarding persistent mobile ARGs and potential pathogens.

Comparative study of bacterial community dynamics in different soils following application of the herbicide atrazine.

Microbial communities in cultivated soils control the fate of pollutants associated with agricultural practice. The present study was designed to explore the response of bacterial communities to the application of the widely-used herbicide atrazine in three different crop fields that differ significantly in their physicochemical structure and nutritional content: the nutrient-rich (with relatively high carbon and nitrogen content) Newe Yaar (NY) and Ha-Ogen (HO) soils and the nutrient-poor, sandy Sde-Eliyahu (SE) soil. The 16 S rRNA gene amplicon sequencing revealed the nutrient poor HO soil differs in its response to atrazine in comparison to the two nutrient-rich soils both in the shortest persistence of atrazine and its effect on community structure and composition. Potential reported bacterial degraders of atrazine such as Pseudomonas, Clostridium and Bacillus were more abundant in contaminated sandy/poor soils (HO) whereas bacteria known for nitrogen cycling such as Azospirillum, Sinorhizobium, Nitrospira and Azohydromonas were significantly more abundant in the nutrient rich contaminated SE soils. No significant increase of potential indigenous degrader Arthrobacter was detected in SE and NY soils whereas a significant increase was recorded with HO soils. An overall shift in bacterial community composition following atrazine application was observed only in the nutrient poor soil. Understanding atrazine persistence and microbiome response to its application of in dependence with soil types serve the design of precision application strategies.

Transformation of 2, 4, 6-trinitrotoluene by Stenotrophomonas strain SG1 under aerobic and anaerobic conditions.

TNT, or 2,4,6-trinitrotoluene, is a common explosive that can contaminate soil and groundwater in production sites, military training areas, and disposal locations. The compound is highly toxic; therefore, there is an urgent need to rehabilitate the impacted environments. Harnessing the microbial ability to biodegrade TNT into environmentally harmless compound(s) is one approach to remediating contaminated sites. In our study, we report on the genomic and metabolic ability of Stenotrophomonas strain SG1 to degrade TNT under aerobic and anaerobic conditions. The bacterial strain SG1 was first isolated as a contaminant from a culture of Diaphorobacter sp. strain DS2 over minimal media supplemented with TNT. The draft genome assembly of strain SG1 is ∼4.7 Mb and is distributed among 358 contigs. The homology search against the custom database of enzymes responsible for TNT biodegradation revealed the presence of three N-ethylmaleimide reductases (NemA) with a defined KEGG ortholog and KEGG pathway of TNT degradation. The presence of respiratory nitrate reductases has also been mapped, which supports denitrification under anaerobic conditions. Experimentally, the TNT transformation rate accelerated when carbon sources, such as sodium acetate, sodium citrate, sodium succinate, sucrose, and glucose (final concentration of 5 mM), were added. Citrate promoted the highest growth and TNT transformation ratio (88.35%) in 120 h. With the addition of 5 mM ammonium chloride, TNT completely disappeared in the citrate and sucrose-containing treatments in 120 h. However, higher biomass was obtained in the sucrose and glucose-containing treatments in 120 h. During incubation, the formation of amino dinitrotoluene isomers, dinitrotoluene isomers, trinitrobenzene, azoxy isomers, diaryl hydroxylamines, and corresponding secondary amines was confirmed by GC/MS and UPLC/MS. 2-Amino-4-nitrotoluene, 4-amino-2-nitrotoluene, and 2-amino-6-nitrotoluene were also identified in the culture supernatant by GC/MS. Under anaerobic conditions, TNT completely disappeared in the citrate and citrate plus nitrate treatments. Since the strain shows the ability to remove TNT, this research should be useful in basic research and practical applications for removing TNT from wastewater.

Bioremediation of Petroleum-Contaminated Soils with Biosurfactant-Producing Degraders Isolated from the Native Desert Soils.

A crude oil spill in 2014 resulted in extensive soil contamination of the hyper arid Evrona Nature Reserve in Israel's Negev Desert. The contaminated soils became highly hydrophobic, threatening the existence of plants in the habitat. We hypothesized that bioaugmenting the soil with indigenous biosurfactant-producing, hydrocarbon-degrading bacteria (HDB) would accelerate the reduction in the soil's hydrophobicity. We aimed to isolate and characterize biosurfactant-producing HDBs from the desert-contaminated soil and test if they can be used for augmenting the soil. Twelve hydrocarbon-degrading strains were isolated, identified as Pseudomonas, and classified as biosurfactants "producing" and "nonproducing". Inoculating 109 CFU/g of "producing" strains into the polluted soil resulted in a 99.2% reduction in soil hydrophobicity within seven days. At the same time, nonproducing strains reduced hydrophobicity by only 17%, while no change was observed in the untreated control. The microbial community in the inoculated soil was dominated by the introduced strains over 28 days, pointing to their persistence. Rhamnolipid biosynthesis gene rhlAB remained persistent in soil inoculated with biosurfactants, indicating in situ production. We propose that the success of the treatment is due to the use of inoculum enriched from the polluted soil.

Modeling-Guided Amendments Lead to Enhanced Biodegradation in Soil.

Extensive use of agrochemicals is emerging as a serious environmental issue coming at the cost of the pollution of soil and water resources. Bioremediation techniques such as biostimulation are promising strategies used to remove pollutants from agricultural soils by supporting the indigenous microbial degraders. Though considered cost-effective and eco-friendly, the success rate of these strategies typically varies, and consequently, they are rarely integrated into commercial agricultural practices. In the current study, we applied metabolic-based community-modeling approaches for promoting realistic in terra solutions by simulation-based prioritization of alternative supplements as potential biostimulants, considering a collection of indigenous bacteria. Efficacy of biostimulants as enhancers of the indigenous degrader Paenarthrobacter was ranked through simulation and validated in pot experiments. A two-dimensional simulation matrix predicting the effect of different biostimulants on additional potential indigenous degraders (Pseudomonas, Clostridium, and Geobacter) was crossed with experimental observations. The overall ability of the models to predict the compounds that act as taxa-selective stimulants indicates that computational algorithms can guide the manipulation of the soil microbiome in situ and provides an additional step toward the educated design of biostimulation strategies. IMPORTANCE Providing the food requirements of a growing population comes at the cost of intensive use of agrochemicals, including pesticides. Native microbial soil communities are considered key players in the degradation of such exogenous substances. Manipulating microbial activity toward an optimized outcome in efficient biodegradation processes conveys a promise of maintaining intensive yet sustainable agriculture. Efficient strategies for harnessing the native microbiome require the development of approaches for processing big genomic data. Here, we pursued metabolic modeling for promoting realistic in terra solutions by simulation-based prioritization of alternative supplements as potential biostimulants, considering a collection of indigenous bacteria. Our genomic-based predictions point at strategies for optimizing biodegradation by the native community. Developing a systematic, data-guided understanding of metabolite-driven targeted enhancement of selected microorganisms lays the foundation for the design of ecologically sound methods for optimizing microbiome functioning.

Antiscalants Used in Seawater Desalination: Biodegradability and Effects on Microbial Diversity.

Antiscalants are organic polymers widely used for scale inhibition in seawater desalination. While they are susceptible to biodegradation, they provide nutrients for bacterial cell growth and energy for the microbes that assimilate and degrade them. This paper shows the biodegradability of three commercial antiscalants (polyacrylate-CA, polyphosphonate-PP, and carboxylated dendrimers-DN) applied in seawater reverse osmosis desalination (SWRO) as well as analyzing the antiscalant's effects on microbial diversity using microbial cultures grown in seawater, under semi-continuous batch conditions. Nutritional uptake and contribution of the antiscalants to microbial growth were investigated by measuring DOC, TDN, NO3-, NO2-, PO4-, NH4+, and TP of the filtered samples of the incubated batch, twice a month, for twelve months. The microbial community was estimated by 16S rRNA sequencing. The main changes in the microbial communities were determined by the incubation period. However, bacterial orders of the antiscalant treatments differed significantly from the control treatment, namely Planctomycetales, Clostridiales, Sphingobacteriales, Rhodobacterales, and Flavobacteriales, and other unclassified bacterial orders, which were found in various relative abundances dependent on incubation times. The results showed the PP antiscalant to be the least biodegradable and to have the least effect on the bacterial community composition compared to the control. This result emphasizes the need to reassess the suitability criteria of antiscalants, and to further monitor their long-term environmental effects.

Inhibition effect of 2,4,6-trinitrotoluene (TNT) on RDX degradation by rhodococcus strains isolated from contaminated soil and water.

2,4,6-trinitrotoluene (TNT) is a highly toxic explosive that contaminates soil and water and may interfere with the degradation of co-occurring compounds, such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). We proposed that TNT may influence RDX-degrading bacteria via either general toxicity or a specific effect on the |RDX degradation mechanisms. Thus, we examined the impact of TNT on RDX degradation by Rhodococcus strains YH1, T7, and YY1, which were isolated from an explosives-polluted environment. Although partly degraded, TNT did not support the growth of any of the strains when used as either sole carbon or sole nitrogen sources, or as carbon and nitrogen sources. The incubation of a mixture of TNT (25 mg/l) and RDX (20 mg/l) completely inhibited RDX degradation. The effect of TNT on the cytochrome P450, catalyzing RDX degradation, was tested in a resting cell experiment, proving that TNT inhibits XplA protein activity. A dose-response experiment showed that the IC50/trans values for YH1, T7, and YY1 were 7.272, 5.098, and 9.140 (mg/l of TNT), respectively, illustrating variable sensitivity to TNT among the strains. The expression of xplA was also strongly suppressed by TNT. Cells that were pre-grown with RDX (allowing xplA expression) and incubated with ammonium chloride, glucose, and TNT, completely transformed into their amino dinitrotoluene isomers and formed azoxy toluene isomers. The presence of oxygen-insensitive nitroreductase that enable reduction of the nitro group in the presence of O2 in the genomes of these strains suggests that they are responsible for TNT transformation in the cultures. The experimental results concluded that TNT has an adverse effect on RDX degradation by the examined strains. It inhibits RDX degradation due to the direct impact on cytochrome P450, xplA, or its expression. The tested strains can transform TNT independently of RDX. Thus, degradation of both compounds is possible if TNT concentrations are below their IC50 values.

Effects of Perchlorate and Other Groundwater Inorganic Co-Contaminants on Aerobic RDX Degradation.

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) pollution is accompanied by other co-contaminants, such as perchlorate and chlorates, which can retard biodegradation. The effects of perchlorate and chlorate on aerobic RDX degradation remain unclear. We hypothesized that they have a negative or no impact on aerobic RDX-degrading bacteria. We used three aerobic RDX-degrading strains-Rhodococcus strains YH1 and T7 and Gordonia YY1-to examine this hypothesis. The strains were exposed to perchlorate, chlorate, and nitrate as single components or in a mixture. Their growth, degradation activity, and gene expression were monitored. Strain-specific responses to the co-contaminants were observed: enhanced growth of strain YH1 and inhibition of strain T7. Vmax and Km of cytochrome P450 (XplA) in the presence of the co-contaminants were not significantly different from the control, suggesting no direct influence on cytochrome P450. Surprisingly, xplA expression increased fourfold in cultures pre-grown on RDX and, after washing, transferred to a medium containing only perchlorate. This culture did not grow, but xplA was translated and active, albeit at lower levels than in the control. We explained this observation as being due to nitrogen limitation in the culture and not due to perchlorate induction. Our results suggest that the aerobic strain YH1 is effective for aerobic remediation of RDX in groundwater.

Strategies for Enhancing in vitro Degradation of Linuron by Variovorax sp. Strain SRS 16 Under the Guidance of Metabolic Modeling.

Phenyl urea herbicides are being extensively used for weed control in both agricultural and non-agricultural applications. Linuron is one of the key herbicides in this family and is in wide use. Like other phenyl urea herbicides, it is known to have toxic effects as a result of its persistence in the environment. The natural removal of linuron from the environment is mainly carried through microbial biodegradation. Some microorganisms have been reported to mineralize linuron completely and utilize it as a carbon and nitrogen source. Variovorax sp. strain SRS 16 is one of the known efficient degraders with a recently sequenced genome. The genomic data provide an opportunity to use a genome-scale model for improving biodegradation. The aim of our study is the construction of a genome-scale metabolic model following automatic and manual protocols and its application for improving its metabolic potential through iterative simulations. Applying flux balance analysis (FBA), growth and degradation performances of SRS 16 in different media considering the influence of selected supplements (potential carbon and nitrogen sources) were simulated. Outcomes are predictions for the suitable media modification, allowing faster degradation of linuron by SRS 16. Seven metabolites were selected for in vitro validation of the predictions through laboratory experiments confirming the degradation-promoting effect of specific amino acids (glutamine and asparagine) on linuron degradation and SRS 16 growth. Overall, simulations are shown to be efficient in predicting the degradation potential of SRS 16 in the presence of specific supplements. The generated information contributes to the understanding of the biochemistry of linuron degradation and can be further utilized for the development of new cleanup solutions without any genetic manipulation.

Regressing SARS-CoV-2 Sewage Measurements Onto COVID-19 Burden in the Population: A Proof-of-Concept for Quantitative Environmental Surveillance.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an RNA virus, a member of the coronavirus family of respiratory viruses that includes severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) and the Middle East respiratory syndrome (MERS). It has had an acute and dramatic impact on health care systems, economies, and societies of affected countries during the past 8 months. Widespread testing and tracing efforts are being employed in many countries in attempts to contain and mitigate this pandemic. Recent data has indicated that fecal shedding of SARS-CoV-2 is common and that the virus RNA can be detected in wastewater. This indicates that wastewater monitoring may provide a potentially efficient tool for the epidemiological surveillance of SARS-CoV-2 infection in large populations at relevant scales. In particular, this provides important means of (i) estimating the extent of outbreaks and their spatial distributions, based primarily on in-sewer measurements, (ii) managing the early-warning system quantitatively and efficiently, and (iii) verifying disease elimination. Here we report different virus concentration methods using polyethylene glycol (PEG), alum, or filtration techniques as well as different RNA extraction methodologies, providing important insights regarding the detection of SARS-CoV-2 RNA in sewage. Virus RNA particles were detected in wastewater in several geographic locations in Israel. In addition, a correlation of virus RNA concentration to morbidity was detected in Bnei-Barak city during April 2020. This study presents a proof of concept for the use of direct raw sewage-associated virus data, during the pandemic in the country as a potential epidemiological tool.

Tracking SARS-CoV-2 RNA through the Wastewater Treatment Process.

Municipal sewage carries degraded and intact viral particles and RNA (ribonucleic acid) of SARS-CoV-2 (severe acute respiratory coronavirus 2), shed by COVID-19 (coronavirus disease 2019) patients, to sewage and eventually to wastewater treatment plants. Proper wastewater treatment can prevent uncontrolled discharges of the virus into the environment. However, the role of different wastewater treatment stages in reducing viral RNA concentrations is, thus far, unknown. Here, we quantified SARS-CoV-2 RNA in raw sewage and during the main stages of the activated sludge process from two wastewater treatment plants in Israel, on three different days during the 2020 COVID-19 outbreak. To reduce the detection limit, samples were concentrated prior to quantification by real-time polymerase chain reaction by a factor of 2-43 using ultrafiltration. On average, ∼1 log RNA removal was attained by each of the primary and secondary treatment steps; however, >100 copies of SARS-CoV-2 RNA/mL remained in the secondary effluents. Following chlorination, SARS-CoV-2 RNA was detected only once, likely due to an insufficient chlorine dose. Our results emphasize the capabilities and limitations of the conventional wastewater treatment process in reducing the SARS-CoV-2 RNA concentration and present preliminary evidence for the importance of tertiary treatment and chlorination in reducing dissemination of the virus to the environment.

Inhibition of perchlorate biodegradation by ferric and ferrous iron.

Previous observations from in-situ biological treatments in the subsurface of a perchlorate-contaminated site revealed multiple reduction processes occurring parallel to perchlorate degradation. Iron reduction was accelerated and correlated with a decline in the efficiency of the in-situ perchlorate reduction. In the current study, we examined the influence of iron forms on perchlorate reduction. A series of kinetic laboratory experiments were conducted, using an indigenous mixed perchlorate-reducing culture, enriched from the polluted soil that was undergoing bioremediation. The results show that ferrous iron was a non-competitive inhibitor with a 41% decrease in µmax for perchlorate reduction. Moreover, chlorate was accumulated in all samples treated with ferrous iron, indicating a disruption to the chlorate reduction step. Ferric iron, however, had less impact on perchlorate degradation with non-competitive inhibition reaching a 23% decrease in µmax. Scanning electron microscopy (SEM) revealed that the presence of ferrous iron in the perchlorate degradation enrichment culture initiated cell encrustation. We propose that during perchlorate reduction and the emission of oxygen from chlorite dismutation, the chemical oxidation of ferrous iron occurred near the bacteria's surface where the enzyme is located, forming an oxidized iron crust layer that can directly affect the perchlorate reduction enzymatic system.

Genome-scale reconstruction of Paenarthrobacter aurescens TC1 metabolic model towards the study of atrazine bioremediation.

Atrazine is an herbicide and a pollutant of great environmental concern that is naturally biodegraded by microbial communities. Paenarthrobacter aurescens TC1 is one of the most studied degraders of this herbicide. Here, we developed a genome scale metabolic model for P. aurescens TC1, iRZ1179, to study the atrazine degradation process at organism level. Constraint based flux balance analysis and time dependent simulations were used to explore the organism's phenotypic landscape. Simulations aimed at designing media optimized for supporting growth and enhancing degradation, by passing the need in strain design via genetic modifications. Growth and degradation simulations were carried with more than 100 compounds consumed by P. aurescens TC1. In vitro validation confirmed the predicted classification of different compounds as efficient, moderate or poor stimulators of growth. Simulations successfully captured previous reports on the use of glucose and phosphate as bio-stimulators of atrazine degradation, supported by in vitro validation. Model predictions can go beyond supplementing the medium with a single compound and can predict the growth outcomes for higher complexity combinations. Hence, the analysis demonstrates that the exhaustive power of the genome scale metabolic reconstruction allows capturing complexities that are beyond common biochemical expertise and knowledge and further support the importance of computational platforms for the educated design of complex media. The model presented here can potentially serve as a predictive tool towards achieving optimal biodegradation efficiencies and for the development of ecologically friendly solutions for pollutant degradation.

Mechanism investigation and stable isotope change during photochemical degradation of tetrabromobisphenol A (TBBPA) in water under LED white light irradiation.

Light driven degradation is very promising for pollutants remediation. In the present work, photochemical reaction of tetrabromobisphenol A (TBBPA) under LED white light (λ > 400 nm) irradiation system was investigated to figure out the TBBPA photochemical degradation pathways and isotope fractionation patterns associated with transformation mechanisms. Results indicated that photochemical degradation of TBBPA would happen only with addition to humic acid in air bubbling but not in N2 bubbling. For photochemical reaction of TBBPA, singlet oxygen (1O2) was found to be important reactive oxygen species for the photochemical degradation of TBBPA. 2,6-Dibromo-4-(propan-2-ylidene)cyclohexa-2,5-dienone and two isopropyl phenol derivatives were identified as the photochemical degradation intermediates by 1O2. 2,6-Dibromo-4-(1-methoxy-ethyl)-phenol was determined as an intermediate via oxidative skeletal rearrangement, reduction and O-methylation. Hydrolysis product hydroxyl-tribromobisphenol A was also observed in the reductive debromination process. In addition, to deeply explore the mechanism, carbon and bromine isotope analysis were performed using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) and gas chromatography-multicollector inductively coupled plasma mass spectrometry (GC/MC/ICPMS) during the photochemical degradation of TBBPA. The results showed that photochemical degradation could not result in statistically significant isotope fractionation, indicated that the bond cleavage of C-C and C-Br were not the rate controlling process. Stable isotope of carbon being not fractionated will be useful for distinguishing the pathways of TBBPA and tracing TBBPA fate in water systems. This work sheds light on photochemical degradation mechanisms of brominated organic contaminants.

Draft Genome Sequences of Rhodococcus sp. Strains YH1 and T7, Isolated from Explosive-Contaminated Environments.

We report the draft genome sequences for Rhodococcus sp. strains YH1 and T7. These strains are both capable of degrading hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and were isolated from explosive-contaminated soil and groundwater, respectively. Further genomic analysis might facilitate an understanding of the degradation of RDX and will contribute to the development of bioremediation methods for polluted soil and groundwater.

Multi-elemental C-Br-Cl isotope analysis for characterizing biotic and abiotic transformations of 1-bromo-2-chloroethane (BCE).

Multi-elemental C-Br-Cl compound-specific isotope analysis was applied for characterizing abiotic and biotic degradation of the environmental pollutant 1-bromo-2-chloroethane (BCE). Isotope effects were determined in the model processes following hydrolytic dehalogenation and dihaloelimination pathways as well as in a microcosm experiment by the microbial culture from the contaminated site. Hydrolytic dehalogenation of BCE under alkaline conditions and by DhaA enzyme resulted in similar dual isotope slopes (ɅC/Br 21.9 ± 4.7 and 19.4 ± 1.8, respectively, and ɅC/Cl ~ ∞). BCE transformation by cyanocobalamin (B12) and by Sulfurospirillum multivorans followed dihaloelimination and was accompanied by identical, within the uncertainty range, dual isotope slopes (ɅC/Br 8.4 ± 1.7 and 7.9 ± 4.2, respectively, and ɅC/Cl 2.4 ± 0.3 and 1.5 ± 0.6, respectively). Changes over time in the isotope composition of BCE from the contaminated groundwater showed only a slight variation in δ13C values and were not sufficient for the elucidation of the BCE degradation pathway in situ. However, an anaerobic microcosm experiment with the enrichment cultures from the contaminated groundwater presented dual isotope slopes similar to the hydrolytic pathway, suggesting that the potential for BCE degradation in situ by the hydrolytic dehalogenation pathway exists in the contaminated site.

Draft Genome Sequence of Gordonia sp. Strain YY1, Isolated from an Explosive-Contaminated Environment.

We report the whole-genome sequence of Gordonia sp. strain YY1, which was isolated from the surface soil in an explosive-contaminated site in Israel and cultivated with hexahydro-1,3,5-trinitro-1,3,5-triazine, i.e., royal demolition explosive (RDX), as a nitrogen source. This genome sequence will improve our understanding of the genes for RDX degradation. In addition, this research will reveal metabolic pathways in order to develop new bioremediation methods for polluted soil and groundwater.