Concurrent anaerobic chromate bio-reduction and pentachlorophenol bio-degradation in a synthetic aquifer

New insights on zero-valent iron permeable reactive barrier for Cr(VI) removal: The function of FeS reaction zone downstream in-situ generated by sulfate-reducing bacteria

The biogeochemical behavior downstream of the zero-valent iron permeable reactive barrier (ZVI-PRB) plays an enormous positive role in the remediation of contaminated-groundwater, but has been completely neglected for a long time. Therefore, this study conducted a 240-day SRB-enhanced ZVI-PRB column experiment, focusing on what exactly happens downstream of ZVI-PRB. Results show that biosulfidation of SRB inside ZVI-PRB prolonged the complete Cr(VI) removal longevity of ZVI-PRB from 38 days to at least 240 days. More importantly, unlike previous studies that focused on improving the performance of ZVI-PRB itself, this study found an in-situ generated FeS reduction reaction zone downstream of the ZVI-PRB. When the ZVI-PRB fails, the downstream reaction zone can continue to play a role in Cr(VI) removal. The maximum Cr(VI) removal capacity of the aquifer media from the reaction zone reached 155.1 mg/kg, which was 39.7 % of commercial ZVI capacity. The reduction zone was further confirmed to be predominantly FeS rather than FeS2. Biogeochemistry occurring within and downstream of ZVI-PRB leads to the formation of FeS. Gene sequencing revealed significantly higher SRB abundance downstream of ZVI-PRB than within the ZVI-PRB. The understanding of the downstream FeS reaction zone provides new insights for more effective remediation using ZVI-PRB.

Groundwater Cr(VI) contamination and remediation: A review from 1999 to 2022

Hexavalent chromium (Cr(VI)) contamination of groundwater has traditionally been an environmental issue of great concern due to its bioaccumulative and highly toxic nature. This paper presents a review and bibliometric analysis of the literature on the interest area "Cr(VI) in groundwater" published in the Web of Science Core Collection from 1999 to 2022. First, information on 203 actual Cr(VI)-contaminated groundwater sites around the world was summarized, and the basic characteristics of the sources and concentrations of contamination were derived. 68.95% of the sites were due to human causes and 56.43% of these sites had Cr(VI) concentrations in the range of 0-10 mg/L. At groundwater sites with high Cr(VI) contamination due to natural causes, 75.00% of the sites had Cr(VI) concentrations less than 0.2 mg/L. A total of 936 papers on "Cr(VI) in groundwater" were retrieved for bibliometric analysis: interest in research on Cr(VI) in groundwater has grown rapidly in recent years; 59.4% of the papers were published in the field of environmental sciences. A systematic review of the progress of studies on the Cr(VI) removal/remediation based on reduction, adsorption and biological processes is presented. Out of 666 papers on Cr(VI) removal/remediation, 512, 274, and 75 papers dealt with the topics of reduction, adsorption, and bioremediation, respectively. In addition, several studies have demonstrated the potential applicability of natural attenuation in the remediation of Cr(VI)-contaminated groundwater. This paper will help researchers to understand and investigate methodological strategies to remove Cr(VI) from groundwater in a more targeted and effective manner.

Bioreduction of chromate in a syngas-based membrane biofilm reactor

This study leveraged synthesis gas (syngas), a renewable resource attainable through the gasification of biowaste, to achieve efficient chromate removal from water. To enhance syngas transfer efficiency, a membrane biofilm reactor (MBfR) was employed. Long-term reactor operation showed a stable and high-level chromate removal efficiency > 95%, yielding harmless Cr(III) precipitates, as visualised by scanning electron microscopy and energy dispersive X-ray analysis. Corresponding to the short hydraulic retention time of 0.25 days, a high chromate removal rate of 80 µmol/L/d was attained. In addition to chromate reduction, in situ production of volatile fatty acids (VFAs) by gas fermentation was observed. Three sets of in situ batch tests and two groups of ex situ batch tests jointly unravelled the mechanisms, showing that biological chromate reduction was primarily driven by VFAs produced from in situ syngas fermentation, whereas hydrogen originally present in the syngas played a minor role. 16 S rRNA gene amplicon sequencing has confirmed the enrichment of syngas-fermenting bacteria (such as Sporomusa), who performed in situ gas fermentation leading to the synthesis of VFAs, and organics-utilising bacteria (such as Aquitalea), who utilised VFAs to drive chromate reduction. These findings, combined with batch assays, elucidate the pathways orchestrating synergistic interactions between fermentative microbial cohorts and chromate-reducing microorganisms. The findings facilitate the development of cost-effective strategies for groundwater and drinking water remediation and present an alternative application scenario for syngas.

Unveiling the inhibitory mechanisms of chromium exposure on microbial reductive dechlorination: Kinetics and microbial responses

Chromium and organochlorine solvents, particularly trichloroethene (TCE), are pervasive co-existing contaminants in subsurface aquifers due to their extensive industrial use and improper disposal practices. In this study, we investigated the microbial dechlorination kinetics under different TCE-Cr(Ⅲ/VI) composite pollution conditions and elucidated microbial response mechanisms based on community shift patterns and metagenomic analysis. Our results revealed that the reductive dechlorinating consortium had high resistance to Cr(III) but extreme sensitivity to Cr(VI) disturbance, resulting in a persistent inhibitory effect on subsequent dechlorination. Interestingly, the vinyl chloride-respiring organohalide-respiring bacteria (OHRB) was notably more susceptible to Cr(III/VI) exposure than the trichloroethene-respiring one, possibly due to inferior competition for growth substrates, such as electron donors. In terms of synergistic non-OHRB populations, Cr(III/VI) exposure had limited impacts on lactate fermentation but significantly interfered with H2-producing acetogenesis, leading to inhibited microbial dechlorination due to electron donor deficiencies. However, this inhibition can be effectively mitigated by the amendment of exogenous H2 supply. Furthermore, being the predominant OHRB, Dehalococcoides have inherent Cr(VI) resistance defects and collaborate with synergistic non-OHRB populations to achieve concurrent bio-detoxication of Cr(VI) and TCE. Our findings expand the understanding of the response patterns of different functional populations towards Cr(III/VI) stress, and provide valuable insights for the development of in situ bioremediation strategies for sites co-contaminated with chloroethene and chromium.

Metagenomic insights into phenanthrene biodegradation in electrical field-governed biofilms for groundwater bioremediation

Electrical fields (EFs)-assisted in-situ bioremediation of petroleum-contaminated groundwater, such as polycyclic aromatic hydrocarbons, has drawn increasing attention. However, the long-term stability, the EFs influence, and metabolic pathways are still poorly understood, hindering the further development of robust technology design. Herein, a series of EFs was applied to the phenanthrene-contaminated groundwater, and the corresponding system performance was investigated. The highest removal capacity of phenanthrene (phe) (7.63 g/(m3·d)) was achieved with EF_0.8 V biofilm at a hydrolytic retention time of 0.5 d. All the biofilms with four EFs exhibited a high removal efficiency of phe over 80% during a 100-d continuous-flow operation. Intermediates analysis revealed the main pathways of phe degradation: phthalate and salicylate via hydroxylation, methylation, carboxylation, and ring cleavage steps. Synergistic effects between phe-degraders (Dechloromonas), fermentative bacteria (Delftia), and electroactive microorganisms (Geobacter) were the main contributors to the complete phe mineralization. Genes encoding various proteins of methyl-accepting (mcp), response regulator (cheABDRY), and type IV pilus (pilABCMQV) were dominant, revealing the importance of cell motility and extracellular electron transfer. Metagenomics analysis unveiled phe-degrading genes, including ring reduction enzymes (bamBCDE), carboxylase of aromatics (ubiD), and methyltransferase protein (ubiE, pcm). These findings offered a molecular understanding of refractory organics' decompositions in EFs-governed biotechnology.

Application of dissimilatory iron-reducing bacteria for the remediation of soil and water polluted with chlorinated organic compounds: Progress, mechanisms, and directions

Chlorinated organic compounds are widely used as solvents, but they are pollutants that can have adverse effects on the environment and human health. Dissimilatory iron-reducing bacteria (DIRB) such as Shewanella and Geobacter have been applied to treat a wide range of halogenated organic compounds due to their specific biological properties. Until now, there has been no systematic review on the mechanisms of direct or indirect degradation of halogenated organic compounds by DIRB. This work summarizes the discussion of DIRB's ability to enhance the dechlorination of reaction systems through different pathways, both biological and biochemical. For biological dechlorination, some DIRB have self-dechlorination capabilities that directly dechlorinate by hydrolysis. Adjustment of dechlorination genes through genetic engineering can improve the dechlorination capabilities of DIRB. DIRB can also adjust the capacity for the microbial community to dechlorinate and provide nutrients to enhance the expression of dechlorination genes in other bacteria. In biochemical dechlorination, DIRB bioconverts Fe(III) to Fe(II), which is capable of dichlorination. On this basis, the DIRB-driven Fenton reaction can efficiently degrade chlorinated organics by continuously maintaining anoxic conditions to generate Fe(II) and oxic conditions to generate H2O2. DIRB can drive microbial fuel cells due to their electroactivity and have a good dechlorination capacity at low levels of energy consumption. The contribution of DIRB to the removal of pesticides, antibiotics and POPs is summarized. Then the DIRB electron transfer mechanism is discussed, which is core to their ability to dechlorinate. Finally, the prospect of future work on the removal of chlorine-containing organic pollutants by DIRB is presented, and the main challenges and further research directions are suggested.

Alkaline-thermal hydrolysate of waste activated sludge as a co-metabolic substrate enhances biodegradation of refractory dye reactive black 5

Aromatic azo dyes possess inherent resistance and are known to be carcinogenic, posing a significant threat to human and ecosystems. Enhancing the biodegradation of azo dyes usually requires the presence of co-metabolic substrates to optimize the process. In addressing the issue of excessive waste activated sludge (WAS) generation, this study explored the potential of utilizing alkaline-thermal hydrolysate of WAS as a co-metabolic substrate to boost the degradation of reactive black 5 (RB5) dyes. The acclimated microbial consortium, when supplemented with the WAS hydrolysate obtained at a hydrolysis temperature of 30 °C, achieved an impressive RB5 decolorization efficiency of 90.3% (pH = 7, 35 °C) with a corresponding COD removal efficiency of 45.0%. The addition of WAS hydrolysate as a co-substrate conferred the consortium with a remarkable tolerance to high dye concentration (1500 mg/L RB5) and salinity levels (4-5%), surpassing the performance of conventional co-metabolic sugars in RB5 degradation. 3D-EEM analysis revealed that protein-like substances rich in tyrosine and tryptophan, present in the WAS hydrolysate, played a crucial role in promoting RB5 biodegradation. Furthermore, the microbial consortium community exhibited an enrichment of dye-degrading species, including Acidovorax, Bordetella, Kerstersia, and Brevundimonas, which dominated the community. Notably, functional genes associated with dye degradation and intermediates were also enriched during the RB5 decolorization and biodegradation process. These findings present a practical strategy for the simultaneous treatment of dye-containing wastewater and recycling of WAS.

Impact of different zero valent iron-based particles on anaerobic microbial dechlorination of 2,4-dichlorophenol: Comparison of dechlorination performance and the underlying mechanism

The integration of iron-based materials and anaerobic microbial consortia has been extensively studied owing to its potential to enhance pollutant degradation. However, few studies have compared how different iron materials enhance the dechlorination of chlorophenols in coupled microbial systems. This study systematically compared the combined performances of microbial community (MC) and iron materials (Fe0/FeS2 +MC, S-nZVI+MC, n-ZVI+MC, and nFe/Ni+MC) for the dechlorination of 2,4-dichlorophenol (DCP) as one representative of chlorophenols. DCP dechlorination rate was significantly higher in Fe0/FeS2 +MC and S-nZVI+MC (1.92 and 1.67 times, with no significant difference between two groups) than in nZVI+MC and nFe/Ni+MC (1.29 and 1.25 times, with no significant difference between two groups). Fe0/FeS2 had better performance for the reductive dechlorination process as compared with other three iron-based materials via the consumption of any trace amount of oxygen in anoxic condition and accelerated electron transfer. On the other hand, nFe/Ni could induce different dechlorinating bacteria as compared to other iron materials. The enhanced microbial dechlorination was mainly due to some putative dechlorinating bacteria (Pseudomonas, Azotobacter, Propionibacterium), and due to improved electron transfer of sulfidated iron particles. Therefore, Fe0/FeS2 as a biocompatible as well as low-cost sulfidated material can be a good alternative for possible engineering applications in groundwater remediation.

Cleanup of Cr(VI)-polluted groundwater using immobilized bacterial consortia via bioreduction mechanisms

Cr(VI) bioreduction has become a remedial alternative for Cr(VI)-polluted site cleanup. However, lack of appropriate Cr(VI)-bioreducing bacteria limit the field application of the in situ bioremediation process. In this study, two different immobilized Cr(VI)-bioreducing bacterial consortia using novel immobilization agents have been developed for Cr(VI)-polluted groundwater remediation: (1) granular activated carbon (GAC) + silica gel + Cr(VI)-bioreducing bacterial consortia (GSIB), and (2) GAC + sodium alginate (SA) + polyvinyl alcohol (PVA) + Cr(VI)-bioreducing bacterial consortia (GSPB). Moreover, two unique substrates [carbon-based agent (CBA) and emulsified polycolloid substrate (EPS)] were developed and used as the carbon sources for Cr(VI) bioreduction enhancement. The microbial diversity, dominant Cr-bioreducing bacteria, and changes of Cr(VI)-reducing genes (nsfA, yieF, and chrR) were analyzed to assess the effectiveness of Cr(VI) bioreduction. Approximately 99% of Cr(VI) could be bioreduced in microcosms with GSIB and CBA addition after 70 days of operation, which caused increased populations of total bacteria, nsfA, yieF, and chrR from 2.9 × 10⁸ to 2.1 × 10¹², 4.2 × 10⁴ to 6.3 × 10¹¹, 4.8 × 10⁴ to 2 × 10¹¹, and 6.9 × 10⁴ to 3.7 × 10⁷ gene copies/L. In microcosms with CBA and suspended bacteria addition (without bacterial immobilization), the Cr(VI) reduction efficiency dropped to 60.3%, indicating that immobilized Cr-bioreducing bacteria supplement could enhance Cr(VI) bioreduction. Supplement of GSPB led to a declined bacterial growth due to the cracking of the materials. The addition of GSIB and CBA could establish a reduced condition, which favored the growth of Cr(VI)-reducing bacteria. The Cr(VI) bioreduction efficiency could be significantly improved through adsorption and bioreduction mechanisms, and production of Cr(OH)₃ precipitates confirmed the occurrence of Cr(VI) reduction. The main Cr-bioreducing bacteria included Trichococcus, Escherichia-Shigella, and Lactobacillus. Results suggest that the developed GSIB bioremedial system could be applied to cleanup Cr(VI)-polluted groundwater effectively.

Bacterial enzymatic degradation of recalcitrant organic pollutants: catabolic pathways and genetic regulations

Contamination of soil and natural water bodies driven by increased organic pollutants remains a universal concern. Naturally, organic pollutants contain carcinogenic and toxic properties threatening all known life forms. The conventional physical and chemical methods employed to remove these organic pollutants ironically produce toxic and non-ecofriendly end-products. Whereas microbial-based degradation of organic pollutants provides an edge, they are usually cost-effective and take an eco-friendly approach towards remediation. Bacterial species, including Pseudomonas, Comamonas, Burkholderia, and Xanthomonas, have the unique genetic makeup to metabolically degrade toxic pollutants, conferring their survival in toxic environments. Several catabolic genes, such as alkB, xylE, catA, and nahAc, that encode enzymes and allow bacteria to degrade organic pollutants have been identified, characterized, and even engineered for better efficacy. Aerobic and anaerobic processes are followed by bacteria to metabolize aliphatic saturated and unsaturated hydrocarbons such as alkanes, cycloalkanes, aldehydes, and ethers. Bacteria use a variety of degrading pathways, including catechol, protocatechuate, gentisate, benzoate, and biphenyl, to remove aromatic organic contaminants such as polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides from the environment. A better understanding of the principle, mechanisms, and genetics would be beneficial for improving the metabolic efficacy of bacteria to such ends. With a focus on comprehending the mechanisms involved in various catabolic pathways and the genetics of the biotransformation of these xenobiotic compounds, the present review offers insight into the various sources and types of known organic pollutants and their toxic effects on health and the environment.

Concurrent reductive decontamination of chromium (VI) and uranium (VI) in groundwater by Fe(0)-based autotrophic bioprocess

The co-presence of chromium (VI) [Cr(VI)] and uranium (VI) [U(VI)] is widely found in groundwater, imposing severe risks on human health. Although zerovalent iron [Fe(0)] supports superb performance for bioreduction of Cr(VI) and U(VI) individually, the biogeochemical process involving their concurrent removal with Fe(0) as electron donor remains unexplored. In the 6-d batch study, 86.1% ± 0.7% of Cr(VI) was preferentially eliminated, while 78.4% ± 0.5% of U(VI) removal was achieved simultaneously. Efficient removal of Cr(VI) (100%) and U(VI) (51.2% ∼ 100%) was also obtained in a continuous 160-d column experiment. As a result, Cr(VI) and U(VI) were reduced to less mobile Cr(III) and insoluble U(IV), respectively. 16 S rRNA sequencing was performed to investigate the dynamics of microbial community. Delftia, Acinetobacter, Pseudomonas and Desulfomicrobium were the major contributors mediating the bioreduction process. The initial Cr(VI) and hydraulic retention time (HRT) incurred pronounced effects on community diversity, which in turn altered the reactor's performance. The enrichment of Cr(VI) resistance (chrA), U(VI) reduction (dsrA) and Fe(II) oxidation (mtrA) genes were observed by reverse transcription qPCR. Cytochrome c, glutathione and NADH as well as VFAs and gas metabolites also involved in the bioprocess. This study demonstrated a promising approach for removing the combined contaminants of Cr(VI) and U(VI) in groundwater.

Independent and synergistic bio-reductions of uranium (VI) driven by zerovalent iron in aquifer

Zerovalent iron [Fe(0)] can donate electron for bioprocess, but microbial uranium (VI) [U(VI)] reduction driven by Fe(0) is still poorly understood. In this study, Fe(0) supported U(VI) bio-reduction was steadily achieved in the 160-d continuous-flow biological column. The maximum removal efficiency and capacity of U(VI) were 100% and 46.4 ± 0.52 g/(m³·d) respectively, and the longevity of Fe(0) increased by 3.09 times. U(VI) was reduced to solid UO₂, while Fe(0) was finally oxidized to Fe(III). Autotrophic Thiobacillus achieved U(VI) reduction coupled to Fe(0) oxidation, verified by pure culture. H₂ produced from Fe(0) corrosion was consumed by autotrophic Clostridium for U(VI) reduction. The detected residual organic intermediates were biosynthesized with energy released from Fe(0) oxidation and utilized by heterotrophic Desulfomicrobium, Bacillus and Pseudomonas to reduce U(VI). Metagenomic analysis found the upregulated genes for U(VI) reduction (e.g., dsrA and dsrB) and Fe(II) oxidation (e.g., CYC1 and mtrA). These functional genes were also transcriptionally expressed. Cytochrome c and glutathione responsible for electron transfer also contributed to U(VI) reduction. This study reveals the independent and synergistic pathways for Fe(0)-dependent U(VI) bio-reduction, providing promising remediation strategy for U(VI)-polluted aquifers.

Conductive Materials on Biocathodes Altered the Electron-Transfer Paths and Modulated γ-HCH Dechlorination and CH4 Production in Microbial Electrochemical Systems

Adding conductive materials to the cathode of a microbial electrochemical system (MES) can alter the route of interspecies electron transfer and the kinetics of reduction reactions. We tested reductive dechlorination of γ-hexachlorocyclohexane (γ-HCH), along with CH₄ production, in MES systems whose cathodes were coated with conductive magnetite nanoparticles (NaFe), biochar (BC), magnetic biochar (FeBC), or anti-conductive silica biochar (SiBC). Coating with NaFe enriched electroactive microorganisms, boosted electro-bioreduction, and accelerated γ-HCH dechlorination and CH₄ production. In contrast, BC only accelerated dechlorination, while FeBC only accelerated methanogenesis, because of their assemblies of functional taxa that selectively transferred electrons to those electron sinks. SiBC, which decreased electro-bioreduction, yielded the highest CH₄ production and increased methanogens and the mcrA gene. This study provides a strategy to selectively control the distribution of electrons between reductive dechlorination and methanogenesis by adding conductive or anti-conductive materials to the MES's cathode. If the goal is to maximize dechlorination and minimize methane generation, then BC is the optimal conductive material. If the goal is to accelerate electro-bioreduction, then the best addition is NaFe. If the goal is to increase the rate of methanogenesis, adding anti-conductive SiBC is the best.

Complete pentachlorophenol biodegradation in a dual-working electrode bioelectrochemical system: Performance and functional microorganism identification

Bioelectrochemical system (BES) can effectively promote the reductive dechlorination of chlorophenols (CPs). However, the complete degradation of CPs with sequential dechlorination and mineralization processes has rarely achieved from the BES. Here, a dual-working electrode BES was constructed and applied for the complete degradation of pentachlorophenol (PCP). Combined with DNA-stable isotope probing (DNA-SIP), the biofilms attached on the anodic and cathodic electrode in the BES were analyzed to explore the dechlorinating and mineralizing microorganisms. Results showed that PCP removal efficiency in the dual-working BES (84% for 21 days) was 4.1 and 4.7 times higher than those of conventional BESs with a single anodic or cathodic working electrode, respectively. Based on DNA-SIP and high-throughput sequencing analysis, the cathodic working electrode harbored the potential dechlorinators (Comamonas, Pseudomonas, Methylobacillus, and Dechlorosoma), and the anodic working enriched the potential intermediate mineralizing bacteria (Comamonas, Stenotrophomonas, and Geobacter), indicating that PCP could be completely degraded under the synergetic effect of these functional microorganisms. Besides, the potential autotrophic functional bacteria that might be involved in the PCP dechlorination were also identified by SIP labeled with ¹³C-NaHCO₃. Our results proved that the dual-working BES could accelerate the complete degradation of PCP and enrich separately the functional microbial consortium for the PCP dechlorination and mineralization, which has broad potential for bioelectrochemical techniques in the treatment of wastewater contaminated with CPs or other halogenated organic compounds.

Wastewater treatment effectiveness is facilitated by crucial bacterial communities in the wetland ecosystem

Microorganisms play essential roles in nutrient removal and biogeochemical cycling during wastewater treatment. However, little is known about the main roles of key functional bacterial communities in wastewater treatment processes. We collected 18 water samples and 15 sediment samples from the six operational subsystems of the constructed wetland, among which the contact oxidation pond, enhanced hybrid biofilm reactor, and central stabilization pond are the main wastewater treatment units in the constructed wetland, and then investigated the bacterial communities using 16S rRNA gene targeting and sequencing to address this knowledge gap. The results indicated that the composition of the bacterial community is closely related to the efficiency of pollutant removal. The abundant carbon metabolism function increased the removal of nitrate‑nitrogen (NO₃^--N) and total nitrogen (TN) by the contact oxidation pond by 89.84 % and 38.91 %, respectively. The overlap of ecological niches and the presence of pathogenic bacteria substantially affect effluent wastewater treatment. Second, NO₃^--N (p < 0.001) was the most important factor driving the bacterial community composition in water and sediments. Furthermore, the positive structure was prevalent in the cooccurrence network of water samples (87.24 %) and sediments (76.53 %) of the wetland, and this positive structure with keystone species was critical for the adaptation of the bacterial community to environmental filtration. In summary, this study reveals the distribution patterns of bacterial communities in different wastewater treatment processes and their driving factors and provides new perspectives on the link between the bacterial community composition and wastewater treatment.

Identification of chlorpyrifos-degrading microorganisms in farmland soils via cultivation-independent and -dependent approaches

Microorganisms have important roles in the bioremediation of organophosphorus pesticides (OPs) in farmland soils. However, the majority of functional microorganisms (>99%) are yet to be cultivated. In this study, magnetic nanoparticle-mediated isolation (MMI) coupled with high-throughput sequencing was applied to identify the microorganisms responsible for chlorpyrifos (CPF) degradation in farmland soils. Various microorganisms have been identified as CPF degraders via MMI, in which the roles of genera Citrobacter, Exiguobacterium, Azoarcus, Azohydromonas and Massilia have not previously been related to CPF degradation. Two organophosphorus hydrolase genes (ophB and ophC) were involved in CPF metabolism in MMI enrichments, compared to only ophB found in the cultivable CPF degrader Alcaligenes L1. Also, a more thorough degradation of CPF was found in MMI enrichments, where 3,5,6-trichloro-2-pyridinol (TCP), O,O-diethyl thiophosphate (DETP), 2,3,5-trichloro-6-methoxypyridine (TMP) and O,O,S-trimethyl phosphorothioate were identified as the biodegradation products. This work suggests that MMI is a promising technology for separating functional microorganisms from complex microbiota, with deeper insight into their ecological functions, providing fundamental knowledge on soil bioremediation strategies.