Application of a novel gene encoding bromophenol dehalogenase from Ochrobactrum sp. T in TBBPA degradation

Biodegradation of nitrate and p-bromophenol using hydrogen-based membrane biofilm reactors in parallel

ABSTRACTP-bromophenol (4-BP) is a toxic halogenated phenolic organic compound. The conventional treatment processes for 4-BP elimination are costly and inefficient, with complete mineralization remaining a challenge for water treatment. To overcome these limitations, we investigated the treatment of 4-BP in a membrane biofilm reactor (MBfR) using hydrogen as an electron donor. The pathway of 4-BP degradation within the H2-MBfR was investigated through long-term operational experiments by considering the effect of nitrate and 4-BP concentrations, hydrogen partial pressure, static experiments, and microbial community diversity, which was studied using 16S rRNA. The results showed that H2-MBfR could quickly remove approximately 100% of 4-BP (up to 20 mg/L), with minimal intermediate product accumulation and 10 mg/L of nitrate continuously reduced. The microbial community structure showed that the presence of H2 created an anaerobic environment, and Thauera was the dominant functional genus involved in the degradation of 4-BP. The genes encoding related enzymes were further enhanced. This study provides an economically viable and environmentally friendly bioremediation technique for water bodies that contain 4-BP and nitrates.

Complete biodegradation of tetrabromobisphenol A through sequential anaerobic reductive dehalogenation and aerobic oxidation

Tetrabromobisphenol A (TBBPA), a common brominated flame retardant and a notorious pollutant in anaerobic environments, resists aerobic degradation but can undergo reductive dehalogenation to produce bisphenol A (BPA), an endocrine disruptor. Conversely, BPA is resistant to anaerobic biodegradation but susceptible to aerobic degradation. Microbial degradation of TBBPA via anoxic/oxic processes is scarcely documented. We established an anaerobic microcosm for TBBPA dehalogenation to BPA facilitated by humin. Dehalobacter species increased with a growth yield of 1.5 × 108 cells per μmol Br- released, suggesting their role in TBBPA dehalogenation. We innovatively achieved complete and sustainable biodegradation of TBBPA in sand/soil columns columns, synergizing TBBPA reductive dehalogenation by anaerobic functional microbiota and BPA aerobic oxidation by Sphingomonas sp. strain TTNP3. Over 42 days, 95.11 % of the injected TBBPA in three batches was debrominated to BPA. Following injection of strain TTNP3 cells, 85.57 % of BPA was aerobically degraded. Aerobic BPA degradation column experiments also indicated that aeration and cell colonization significantly increased degradation rates. This treatment strategy provides valuable technical insights for complete TBBPA biodegradation and analogous contaminants.

Effects of biochar immobilization of Serratia sp. F4 OR414381 on bioremediation of petroleum contamination and bacterial community composition in loess soil

Petroleum hydrocarbons pose a significant threat to human health and the environment. Biochar has increasingly been utilized for soil remediation. This study investigated the potential of biochar immobilization using Serratia sp. F4 OR414381 for the remediation of petroleum-contaminated soil through a pot experiment conducted over 90 days. The treatments in this study, denoted as IMs (maize straw biochar-immobilized Serratia sp. F4), degraded 82.5% of the total petroleum hydrocarbons (TPH), 59.23% of the aromatic, and 90.1% of the saturated hydrocarbon fractions in the loess soils. During remediation, the soil pH values decreased from 8.76 to 7.33, and the oxidation-reduction potential (ORP) increased from 156 to 229 mV. The treatment-maintained soil nutrients of the IMs were 138.94 mg/kg of NO3- -N and 92.47 mg/kg of available phosphorus (AP), as well as 11.29% of moisture content. The activities of soil dehydrogenase (SDHA) and catalase (CAT) respectively increased by 14% and 15 times compared to the CK treatment. Three key petroleum hydrocarbon degradation genes, including CYP450, AJ025, and xylX were upregulated following IMs treatment. Microbial community analysis revealed that a substantial microbial population of 1.01E+ 09 cells/g soil and oil-degrading bacteria such as Salinimicrobium, Saccharibacteria_genera_incertae_sedis, and Brevundimonas were the dominant genera in IMs treatment. This suggests that the biochar immobilized on Serratia sp. F4 OR414381 improves soil physicochemical properties and enhances interactions among microbial populations, presenting a promising and environmentally friendly approach for the stable and efficient remediation of petroleum-contaminated loess soil.

Biodegradation of phenolic pollutants and bioaugmentation strategies: A review of current knowledge and future perspectives

The widespread use of phenolic compounds renders their occurrence in various environmental matrices, posing ecological risks especially the endocrine disruption effects. Biodegradation-based techniques are efficient and cost-effective in degrading phenolic pollutants with less production of secondary pollution. This review focuses on phenol, 4-nonylphenol, 4-nitrophenol, bisphenol A and tetrabromobisphenol A as the representatives, and summarizes the current knowledge and future perspectives of their biodegradation and the enhancement strategy of bioaugmentation. Biodegradation and isolation of degrading microorganisms were mainly investigated under oxic conditions, where phenolic pollutants are typically hydroxylated to 4-hydroxybenzoate or hydroquinone prior to ring opening. Bioaugmentation efficiencies of phenolic pollutants significantly vary under different application conditions (e.g., increased degradation by 10-95% in soil and sediment). To optimize degradation of phenolic pollutants in different matrices, the factors that influence biodegradation capacity of microorganisms and performance of bioaugmentation are discussed. The use of immobilization strategy, indigenous degrading bacteria, and highly competent exogenous bacteria are proposed to facilitate the bioaugmentation process. Further studies are suggested to illustrate 1) biodegradation of phenolic pollutants under anoxic conditions, 2) application of microbial consortia with synergistic effects for phenolic pollutant degradation, and 3) assessment on the uncertain ecological risks associated with bioaugmentation, resulting from changes in degradation pathway of phenolic pollutants and alterations in structure and function of indigenous microbial community.

Effect of the Application of Ochrobactrum sp.-Immobilised Biochar on the Remediation of Diesel-Contaminated Soil

The immobilisation of bacteria on biochar has shown potential for enhanced remediation of petroleum hydrocarbon-contaminated soil. However, there is a lack of knowledge regarding the effect of bacterial immobilisation on biosolids-derived biochar for the remediation of diesel-contaminated soil. This current study aimed to assess the impact of the immobilisation of an autochthonous hydrocarbonoclastic bacteria, Ochrobacterium sp. (BIB) on biosolids-derived biochar for the remediation of diesel-contaminated soil. Additionally, the effect of fertiliser application on the efficacy of the BIB treatment was investigated. Biochar (BC) application alone led to significantly higher hydrocarbon removal than the control treatment at all sampling times (4887-11,589 mg/kg higher). When Ochrobacterium sp. was immobilised on biochar (BIB), the hydrocarbon removal was greater than BC by 5533 mg/kg and 1607 mg/kg at weeks 10 and 22, respectively. However, when BIB was co-applied with fertiliser (BIBF), hydrocarbon removal was lower than BIB alone by 6987-11,767 mg/kg. Quantitative PCR (q-PCR) analysis revealed that the gene related to Ochrobacterium sp. was higher in BIB than in the BC treatment, which likely contributed to higher hydrocarbon removal in the BIB treatment. The results of the q-PCR analysis for the presence of alkB genes and FTIR analysis suggest that the degradation of alkane contributed to hydrocarbon removal. The findings of this study demonstrate that bacterial immobilisation on biosolids-derived biochar is a promising technique for the remediation of diesel-contaminated soil. Future studies should focus on optimising the immobilisation process for enhanced hydrocarbon removal.

Biodegradation of selected aminophosphonates by the bacterial isolate Ochrobactrum sp. BTU1

Aminophosphonates, like glyphosate (GS) or metal chelators such as ethylenediaminetetra(methylenephosphonic acid) (EDTMP), are released on a large scale worldwide. Here, we have characterized a bacterial strain capable of degrading synthetic aminophosphonates. The strain was isolated from LC/MS standard solution. Genome sequencing indicated that the strain belongs to the genus Ochrobactrum. Whole-genome classification using pyANI software to compute a pairwise ANI and other metrics between Brucella assemblies and Ochrobactrum contigs revealed that the bacterial strain is designated as Ochrobactrum sp. BTU1. Degradation batch tests with Ochrobactrum sp. BTU1 and the selected aminophosphonates GS, EDTMP, aminomethylphosphonic acid (AMPA), iminodi(methylene-phosphonic) (IDMP) and ethylaminobis(methylenephosphonic) acid (EABMP) showed that the strain can use all phosphonates as sole phosphorus source during phosphorus starvation. The highest growth rate was achieved with AMPA, while EDTMP and GS were least supportive for growth. Proteome analysis revealed that GS degradation is promoted by C-P lyase via the sarcosine pathway, i.e., initial cleavage at the C-P bond. We also identified C-P lyase to be responsible for degradation of EDTMP, EABMP, IDMP and AMPA. However, the identification of the metabolite ethylenediaminetri(methylenephosphonic acid) via LC/MS analysis in the test medium during EDTMP degradation indicates a different initial cleavage step as compared to GS. For EDTMP, it is evident that the initial cleavage occurs at the C-N bond. The detection of different key enzymes at regulated levels, form the bacterial proteoms during EDTMP exposure, further supports this finding. This study illustrates that widely used and structurally more complex aminophosphonates can be degraded by Ochrobactrum sp. BTU1 via the well-known degradation pathways but with different initial cleavage strategy compared to GS.

Aerobic Microbial Transformation of Fluorinated Liquid Crystal Monomer: New Pathways and Mechanism

Fluorinated liquid crystal monomers (FLCMs) have been suggested as emerging contaminants, raising global concern due to their frequent occurrence, potential toxic effects, and endurance capacity in the environment. However, the environmental fate of the FLCMs remains unknown. To fill this knowledge gap, we investigated the aerobic microbial transformation mechanisms of an important FLCM, 4-[difluoro(3,4,5-trifluorophenoxy)methyl]-3, 5-difluoro-4'-propylbiphenyl (DTMDPB), using an enrichment culture termed as BG1. Our findings revealed that 67.5 ± 2.1% of the initially added DTMDPB was transformed in 10 days under optimal conditions. A total of 14 microbial transformation products obtained due to a series of reactions (e.g., reductive defluorination, ether bond cleavage, demethylation, oxidative hydroxylation and aromatic ring opening, sulfonation, glucuronidation, O-methylation, and thiolation) were identified. Consortium BG1 harbored essential genes that could transform DTMDPB, such as dehalogenation-related genes [e.g., glutathione S-transferase gene (GST), 2-haloacid dehalogenase gene (2-HAD), nrdB, nuoC, and nuoD]; hydroxylating-related genes hcaC, ubiH, and COQ7; aromatic ring opening-related genes ligB and catE; and methyltransferase genes ubiE and ubiG. Two DTMDPB-degrading strains were isolated, which are affiliated with the genus Sphingopyxis and Agromyces. This study provides a novel insight into the microbial transformation of FLCMs. The findings of this study have important implications for the development of bioremediation strategies aimed at addressing sites contaminated with FLCMs.

Efficient degradation of tetrabromobisphenol A using peroxymonosulfate oxidation activated by a novel nano-CuFe2O4@coconut shell biochar catalyst

In this study, a novel bimetallic complexation-curing nucleation-anaerobic calcination method was developed to synthesize a nano-CuFe2O4@coconut shell biochar (CuFe2O4@CSBC) catalyst to activate peroxymonosulfate for degradation of tetrabromobisphenol A (TBBPA). The reaction processes of the TBBPA on CuFe2O4@CSBC have been investigated using in situ characterization and metal leaching. The effects of initial reaction conditions and degradation mechanism were investigated. Greater than 99% degradation of TBBPA at 10 mg L-1 was achieved in 30 min under the condition of pH 11, a total organic carbon removal rate of up to 70.67% was achieved and the degradation efficiency was 90% after 5 cycles of CuFe2O4@CSBC use. The degradation was in a second-order reaction at a constant of 0.797 M-1 min-1 (R2 = 0.993). The degradation was attributed to the main active species (SO4·-≈·OH < 1O2), and the surface active site of CuFe2O4@CSBC was the key role. The degradation process involved three main degradation pathways. Path A: ·OH attacked the C-Br bonds (TBBPA→TriBBPA→DBBPA→MBBPA→BPA); Path B: Hydroxylation and decarboxylation; Path C: Dehydrocoupling of TBBPA. What's more, the practical application of the system was very positive, achieved >77% degradation in sewage and industrial wastewater.

Efficient NADPH-dependent dehalogenation afforded by a self-sufficient reductive dehalogenase

Reductive dehalogenases are corrinoid and iron-sulfur cluster-containing enzymes that catalyze the reductive removal of a halogen atom. The oxygen-sensitive and membrane-associated nature of the respiratory reductive dehalogenases has hindered their detailed kinetic study. In contrast, the evolutionarily related catabolic reductive dehalogenases are oxygen tolerant, with those that are naturally fused to a reductase domain with similarity to phthalate dioxygenase presenting attractive targets for further study. We present efficient heterologous expression of a self-sufficient catabolic reductive dehalogenase from Jhaorihella thermophila in Escherichia coli. Combining the use of maltose-binding protein as a solubility-enhancing tag with the btuCEDFB cobalamin uptake system affords up to 40% cobalamin occupancy and a full complement of iron-sulfur clusters. The enzyme is able to efficiently perform NADPH-dependent dehalogenation of brominated and iodinated phenolic compounds, including the flame retardant tetrabromobisphenol, under both anaerobic and aerobic conditions. NADPH consumption is tightly coupled to product formation. Surprisingly, corresponding chlorinated compounds only act as competitive inhibitors. Electron paramagnetic resonance spectroscopy reveals loss of the Co(II) signal observed in the resting state of the enzyme under steady-state conditions, suggesting accumulation of Co(I)/(III) species prior to the rate-limiting step. In vivo reductive debromination activity is readily observed, and when the enzyme is expressed in E. coli strain W, supports growth on 3-bromo-4-hydroxyphenylacetic as a sole carbon source. This demonstrates the potential for catabolic reductive dehalogenases for future application in bioremediation.

Detoxification of fluoroglucocorticoid by Acinetobacter pittii C3 via a novel defluorination pathway with hydrolysis, oxidation and reduction: Performance, genomic characteristics, and mechanism

Biological dehalogenation degradation was an important detoxification method for the ecotoxicity and teratogenic toxicity of fluorocorticosteroids (FGCs). The functional strain Acinetobacter pittii C3 can effectively biodegrade and defluorinate to 1 mg/L Triamcinolone acetonide (TA), a representative FGCs, with 86 % and 79 % removal proportion in 168 h with the biodegradation and detoxification kinetic constant of 0.031/h and 0.016/h. The dehalogenation and degradation ability of strain C3 was related to its dehalogenation genomic characteristics, which manifested in the functional gene expression of dehalogenation, degradation, and toxicity tolerance. Three detoxification mechanisms were positively correlated with defluorination pathways through hydrolysis, oxidation, and reduction, which were regulated by the expression of the haloacid dehalogenase (HAD) gene (mupP, yrfG, and gph), oxygenase gene (dmpA and catA), and reductase gene (nrdAB and TgnAB). Hydrolysis defluorination was the most critical way for TA detoxification metabolism, which could rapidly generate low-toxicity metabolites and reduce toxic bioaccumulation due to hydrolytic dehalogenase-induced defluorination. The mechanism of hydrolytic defluorination was that the active pocket of hydrolytic dehalogenase was matched well with the spatial structure of TA under the adjustment of the hydrogen bond, and thus induced molecular recognition to promote the catalytic hydrolytic degradation of various amino acid residues. This work provided an effective bioremediation method and mechanism for improving defluorination and detoxification performance.

Efficient biodegradation of tetrabromobisphenol A by the novel strain Enterobacter sp. T2 with good environmental adaptation: Kinetics, pathways and genomic characteristics

T2, a gram-positive bacterium capable of rapidly degrading tetrabromobisphenol A (TBBPA), and affiliated with the genus Enterobacter, was isolated for the first time from sludge that had been contaminated for several years. The TBBPA degradation data fitted the first-order model well. Under optimal conditions (pH of 7, temperature of 31 °C, TBBPA concentration of 5 mg L^-1, and inoculum size of 5%), 99.4% of the initially added TBBPA was degraded after 48 h. TBBPA degradation fitted the first-order model with the half-life of 3.3 h. These results illustrated that the TBBPA degradation capability of strain T2 was significantly better than that of previously reported bacteria. A total of 17 intermediates were detected, among which five were reported for the first time. Whole-genome sequencing revealed that strain T2 had a chromosome with the total length of 4 854 376 bp and a plasmid with the total length of 21 444 bp. It harbored essential genes responsible for debromination, such as cyp450, gstB, gstA, and HADH, and genes responsible for subsequent complete mineralization, such as bioC, yrrM, Tam, and Ubil. A key protein of haloacid dehalogenases responsible for the biodegradation of TBBPA may also be involved in the regulation of TBBPA degradation in natural environment. In soil bioremediation experiments, strain T2 showed excellent environmental adaptation. It was able to biodegrade TBBPA and its typical intermediate bisphenol A efficiently. Therefore, it could potentially be applied to treat TBBPA-contaminated sites.

Tetrabromobisphenol A (TBBPA) anaerobic biodegradation occurs during acidogenesis

This is the first study to bring evidence on the anaerobic biodegradation of TBBPA occurring during acidogenesis in domestic sewage at environmentally relevant concentrations by complex microbial communities. This was accomplished by continuously operating two anaerobic structured bed reactors (ASTBR) for over 100 days under acidogenic (Acidogenic Reactor, AR) and multistep methanogenic (Methanogenic Reactor, MR) conditions. In the AR, the temporal carbohydrates consumption and the acetic acid production were strongly correlated with TBBPA removal by the Pearson's test. The spatial concentration of TBBPA and carbohydrates along the MR and the kinetic degradation profiles corroborate the AR results. It is hypothesized that TBBPA biodegradation in the studied conditions occurs during acidogenesis via the cometabolism supported by non-specific enzymes and the metabolism (dehalorespiration) established by electrons donors such as H₂, which are both produced during the macrocomponents breakdown in the early stages of the anaerobic digestion. The TBBPA mass balance showed that approximately 86.8 ± 0.05% and 97 ± 0.01% of the removed TBBPA was biodegraded in the AR and MR, respectively. Furthermore, TBBPA biodegradation went further than reductive debromination as total phenols were detected in the reactors' effluent.

Microbial community diversity and composition in river sediments contaminated with tetrabromobisphenol A and copper

The microbial community composition in aquatic ecosystems have received increased attention. However, the knowledge gap relative to the responses of bacterial, archaeal and fungal communities in co-contaminated river sediments remain poorly studied. Here, we investigated the changes of tetrabromobisphenol A (TBBPA) and copper (Cu) concentrations and the responses of microbial communities in co-contaminated sediments during long-term incubation. TBBPA concentrations significantly decreased over time, whereas Cu concentrations remained relatively stable over the 60-day incubation. Abundances of the bacterial 16S rRNA, archaeal 16S rRNA and fungal ITS genes ranged from 6.53 × 10⁶ to 1.26 × 10⁹ copies g^-1, 1.12 × 10⁶ to 5.47 × 10⁶ copies g^-1 and 5.33 × 10³ to 7.51 × 10⁴ copies g^-1 in the samples, respectively. A total of 11, 6 and 5 bacterial, archaeal and fungal phyla were identified across all samples. Bacterial, archaeal and fungal communities mainly consisted of members from the phyla Proteobacteria and Acidobacteria, Methanomicrobia and Woesearchaeia as well as Agaricales and Helotiales, respectively. Fungal communities showed a stronger response to pollutant addition after a long incubation compared with bacterial and archaeal communities. The variance analysis results revealed that the bacterial, archaeal and fungal microbial communities of all treatments were distinctly distributed into two separated clusters according to incubation time. However, the three microbial communities did not significantly change in response to pollutant types, which was consistent with variation in relative abundances of the three microbial communities. These findings improve our understanding of the ecotoxicological effects of co-exposure on sediment microbial communities.

Microbial Enzymes Used in Bioremediation

Emerging pollutants in nature are linked to various acute and chronic detriments in biotic components and subsequently deteriorate the ecosystem with serious hazards. Conventional methods for removing pollutants are not efficient; instead, they end up with the formation of secondary pollutants. Significant destructive impacts of pollutants are perinatal disorders, mortality, respiratory disorders, allergy, cancer, cardiovascular and mental disorders, and other harmful effects. The pollutant substrate can recognize different microbial enzymes at optimum conditions (temperature/pH/contact time/concentration) to efficiently transform them into other rather unharmful products. The most representative enzymes involved in bioremediation include cytochrome P450s, laccases, hydrolases, dehalogenases, dehydrogenases, proteases, and lipases, which have shown promising potential degradation of polymers, aromatic hydrocarbons, halogenated compounds, dyes, detergents, agrochemical compounds, etc. Such bioremediation is favored by various mechanisms such as oxidation, reduction, elimination, and ring-opening. The significant degradation of pollutants can be upgraded utilizing genetically engineered microorganisms that produce many recombinant enzymes through eco-friendly new technology. So far, few microbial enzymes have been exploited, and vast microbial diversity is still unexplored. This review would also be useful for further research to enhance the efficiency of degradation of xenobiotic pollutants, including agrochemical, microplastic, polyhalogenated compounds, and other hydrocarbons.

Hazardous wastes treatment technologies

A review of the literature published in 2019 on topics related to hazardous waste management in water, soils, sediments, and air. The review covered treatment technologies applying physical, chemical, and biological principles for the remediation of contaminated water, soils, sediments, and air. PRACTICAL POINTS: This report provides a review of technologies for the management of waters, wastewaters, air, sediments, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) in three scientific areas of physical, chemical, and biological methods. Physical methods for the management of hazardous wastes including general adsorption, sand filtration, coagulation/flocculation, electrodialysis, electrokinetics, electro-sorption ( capacitive deionization, CDI), membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non-thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed. Chemical methods including ozone-based, hydrogen peroxide-based, potassium permanganate processes, and Fenton and Fenton-like process were reviewed. Biological methods such as aerobic, anoxic, anaerobic, bioreactors, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed. Case histories were reviewed in four areas including contaminated sediments, contaminated soils, mixed industrial solid wastes and radioactive wastes.

Genomic Characterization of Antimicrobial Resistance, Virulence, and Phylogeny of the Genus Ochrobactrum

Ochrobactrum is a ubiquitous Gram-negative microorganism, mostly found in the environment, which can cause opportunistic infections in humans. It is almost uniformly resistant to penicillins and cephalosporins through an AmpC-like β-lactamase enzyme class (OCH). We studied 130 assembled genomes, of which 5 were animal-derived isolates recovered in Israel, and 125 publicly available genomes. Our analysis focused on antimicrobial resistance (AMR) genes, virulence genes, and whole-genome phylogeny. We found that 76% of Ochrobactrum genomes harbored a bla_OCH β-lactamase gene variant, while 7% harbored another AmpC-like gene. No virulence genes other than lipopolysaccharide-associated genes were found. Core genome multilocus sequence typing clustered most samples to known species, but neither geographical clustering nor isolation source clustering were evident. When analyzing the distribution of different bla_OCH variants as well as of the bla_OCH-deficient samples, a clear phylogenomic clustering was apparent for specific species. The current analysis of the largest collection to date of Ochrobactrum genomes sheds light on the resistome, virulome, phylogeny, and species classification of this increasingly reported human pathogen. Our findings also suggest that Ochrobactrum deserves further characterization to underpin its evolution, taxonomy, and antimicrobial resistance.

Proteomic mechanism of decabromodiphenyl ether (BDE-209) biodegradation by Microbacterium Y2 and its potential in remediation of BDE-209 contaminated water-sediment system

The investigation of BDE-209 degradation by Microbacterium Y2 under different condition was conducted. Cell membrane permeability, cell surface hydrophobicity (CSH), membrane potential (MP) and reactive oxygen species (ROS) production were altered under BDE-209 stress. Eleven debrominated congeners were identified, suggesting that BDE-209 biodegradation by Microbacterium Y2 was dominantly a successive debromination process. Proteome analysis showed that the overexpression of haloacid dehalogenases, glutathione S-transferases (GSTs) and ATP-binding cassette (ABC) transporters might occupy important roles in BDE-209 biotransformation. Meanwhile, heat shock proteins (HSPs), ribonuclease E, oligoribonuclease (Orn) and ribosomal protein were activated to counter the BDE-209 toxicity. The up-regulated pyruvate dehydrogenase E1 component beta subunit and dihydrolipoamide dehydrogenase suggested that the pyruvate metabolism pathway was activated. Bioaugmentation of BDE-209 polluted water-sediments system with Microbacterium Y2 could efficiently improve BDE-209 removal. The detection of total 16S rRNA genes in treatment system suggested that Microbacterium (25.6 %), Luteimonas (14.3 %), Methylovorus (12.6 %), Hyphomicrobium (9.2 %) were the dominant genera and PICRUSt results further revealed that the diminution of BDE-209 was owed to cooperation between the introduced bacteria and aboriginal ones.

Heterologous expression of the tetracycline resistance gene tetX to enhance degradability and safety in doxycycline degradation

Microbial remediation has the potential to inexpensively yet effectively decontaminate and restore contaminated environments, but the virulence of pathogens and risk of resistance gene transmission by microorganisms during antibiotic removal often limit its implementation. Here, a cloned tetX gene with clear evolutionary history was expressed to explore doxycycline (DOX) degradation and resistance variation during the degradation process. Phylogenetic analysis of tetX genes showed high similarity with those of pathogenic bacteria, such as Riemerella sp. and Acinetobacter sp. Successful tetX expression was performed in Escherichia coli and confirmed by SDS-PAGE and Western blot. Our results showed that 95.0 ± 1.0% of the DOX (50 mg/L) was degraded by the recombinant strain (ETD-1 with tetX) within 48 h, which was significantly higher than that for the control (38.9 ± 8.7%) and the empty plasmid bacteria (8.8 ± 5.1%) (P < 0.05). The tetX gene products in ETD-1 cell extracts also exhibited an efficient DOX degradation ability, with a degradation rate of 80.5 ± 1.2% at 168 h. Furthermore, there was no significant proliferation of the tetX resistance gene during DOX degradation (P > 0.05). The efficient and safe DOX-degrading capacity of the recombinant strain ETD-1 makes it valuable and promising for antibiotic removal in the environment.

Biodegradation of typical BFRs 2,4,6-tribromophenol by an indigenous strain Bacillus sp. GZT isolated from e-waste dismantling area through functional heterologous expression

Legacy wastewater contaminants from e-waste dismantling process such as 2,4,6-tribromophenol (TBP), one of the most widely used brominated flame retardants (BFRs), have raised concern owing to their toxicity and recalcitrance. Our previously isolated Bacillus sp. GZT from river sludge in e-waste dismantling area is a good candidate for bioremediation of BFRs contaminated sites considering its remarkable degradability of TBP and its intermediates. However, there exists a new challenge because bio-degrader cannot produce enough biomass or metabolic activity to cleanup TBP in practice complex environment. Here, we heterologously expressed and functionally characterized the genes and enzymes responsible for TBP degradation to examine the feasibility of enhancing the ability of this microorganism to detoxify TBP. Results demonstrated that five recombinant strains containing functional genes, designated tbpA, tbpB, tbpC, tbpD, and tbpE, become more tolerant toward a wide range of brominated compounds than the nontransgenic strain. Cytochrome P450 reductase encoded by tbpA gene could greatly increase efficiency to remove TBP (98.8%), as compared to wild-type strain GZT (93.2%). Its debromination intermediates 2,4-dibromophenol, 2,6-dibromo-4-methylphenol and 2-bromophenol were significantly metabolized by halophenol dehalogenases encoded by tbpB, tbpC, and tbpD, respectively. Finally, under the function of tbpE gene encoding enzyme, further debrominated product (phenol) was dramatically detoxified. To reduce the risk of these xenobiotics, the expression of these genes can be induced and significantly up-regulated during exposure to them. These results open broad scope for future study in developing genetic engineering technologies for more efficient remediation wastewater of e-waste recycling sites contaminated with TBP, which would certainly be important steps to lower TBP exposures and prevent potential health effects.

Purification, molecular characterization and metabolic mechanism of an aerobic tetrabromobisphenol A dehalogenase, a key enzyme of halorespiration in Ochrobactrum sp. T

Due to the detoxification of tetrabromobisphenol A (TBBPA) varies from different bacterial strains and depends on their specific enzymatic machinery, it is necessary to understand them for potential in situ bioremediation application. The special ability of our previously isolated Ochrobactrum sp. T to simultaneously debrominate and aerobic mineralize TBBPA urgent us to continuously study its degradation molecular mechanism. Herein, the purification and characterization of the dehalogenase which can debrominate TBBPA was investigated based on its corresponding encoding gene tbbpaA. Results showed that an enzyme with molecular mass of 117 kDa, K_m of 26.6 μM and V_max of 0.133 μM min^-1 mg^-1 was purified and designated as bromophenol dehalogenase. It was the only detected dehalogenase which exhibited TBBPA degradation ability (78%). Moreover, its activity was significantly enhanced by adding NADPH or methyl viologen to the reaction solution. The high similarity of substrate spectrum between the dehalogenase from the recombinant strain and the wild strain further indicated that it was the main dehalogenase responsible for the debromination in wild strain. Based on three identified metabolites, a metabolic pathway of TBBPA by purified enzyme under oxic condition was proposed. This study provides an excellent dehalogenase candidate for mechanistic study of aerobic dehalogenation of brominated aromatic compound.

Aerobic cometabolism of tetrabromobisphenol A by marine bacterial consortia

The coastal environments worldwide are subjected to increasing TBBPA contamination, but current knowledge on aerobic biodegradability of this compound by marine microbes is lacking. The aerobic removal of TBBPA using marine consortia under eight different cometabolic conditions was investigated here. Results showed that the composition and diversity of the TBBPA-degrading consortia had diverged after 120-day incubation. Pseudoalteromonas, Alteromonas, Glaciecola, Thalassomonas, and Limnobacter were the dominant genera in enrichment cultures. Furthermore, a combination of beef extract- and peptone-enriched marine consortia exhibited higher TBBPA removal efficiency (approximately 60%) than the other substrate amendments. Additionally, Alteromonas macleodii strain GCW was isolated from a culture of TBBPA-degrading consortium. This strain exhibited about 90% of degradation efficiency toward TBBPA (10 mg L^-1) after 10 days of incubation under aerobic cometabolic conditions. The intermediates in the degradation of TBBPA by A. macleodii strain GCW were analyzed and the degradation pathways were proposed, involving β-scission, debromination, and nitration routes.