Metagenomic analysis for taxonomic and functional potential of Polyaromatic hydrocarbons (PAHs) and Polychlorinated biphenyl (PCB) degrading bacterial communities in steel industrial soil

Metagenomic approaches in bioremediation of environmental pollutants

Metagenomics has emerged as a pivotal tool in bioremediation, providing a deeper understanding of the structure and function of the microbial communities involved in pollutant degradation. By circumventing the limitations of traditional culture-based methods, metagenomics enables comprehensive analysis of microbial ecosystems and facilitates the identification of new genes and metabolic pathways that are critical for bioremediation. Advanced sequencing technologies combined with computational and bioinformatics approaches have greatly enhanced our ability to detect sources of pollution and monitor dynamic changes in microbial communities during the bioremediation process. These tools enable the precise identification of key microbial players and their functional roles, and provide a deeper understanding of complex biodegradation networks. The integration of artificial intelligence (AI) with machine learning algorithms has accelerated the process of discovery of novel genes associated with bioremediation and has optimized metabolic pathway prediction. Novel strategies, including sequencing techniques and AI-assisted analysis, have the potential to revolutionize bioremediation by enabling the development of highly efficient, targeted, and sustainable remediation strategies for various contaminated environments. However, the complexity of microbial interactions, data interpretation, and high cost of these advanced technologies remain challenging. Future research should focus on improving computational tools, reducing costs, and integrating multidisciplinary approaches to overcome these limitations.

Deciphering Indigenous Bacterial Diversity of Co-Polluted Sites to Unravel Its Bioremediation Potential: A Metagenomic Approach

Polluted drains across the globe are affected due to reckless disposal of untreated industrial effluents resulting in significant water pollution affecting microbial community structure/dynamics. To elucidate this, polluted samples were collected from Budha Nala (BN) drain, Tung Dhab (TD) drain, and wastewater treatment plant (WWTP) receiving an inflow of organic pollutants as well as heavy metals due to anthropogenic activities. The sample of unpolluted pristine soil (PS) was used as control, as there is no history of usage of organic chemicals at this site. The bacterial diversity of these samples was sequenced using the Illumina MiSeq platform by amplifying the V3/V4 region of 16S rRNA. The majority of operational taxonomic unit (OTUs) at polluted sites belonged to phyla Proteobacteria specifically Gammaproteobacteria class, followed by Actinobacteria, Bacteriodetes, Chloroflexi, Firmicutes, Planctomycetes, WS6, and TM7, whereas unpolluted site revealed the prevalence of Proteobacteria followed by Actinobacteria, Planctomycetes, Firmicutes, Acidobacteria, Chloroflexi, Bacteroidetes, Verrucomicrobia, and Nitrospirae. The data sets decode unclassified species of the phyla Proteobacteria, Bacteriodetes, Chloroflexi, Firmicutes, and WS6, along with some unclassified bacterial species. The study provided a comparative study of changed microbial community structure, their possible functions across diverse geographical locations, and identifying specific bacterial genera as pollution bio-indicators of aged polluted drains.

Assembly patterns and key taxa of bacterial communities in the rhizosphere soil of moso bamboo (Phyllostachys pubescens) under different Cd and Pb pollution

Moso bamboo is excellent candidate for cadmium (Cd)/lead (Pb) phytoremediation, while rhizosphere microbiome has significant impact on phytoremediation efficiency of host plant. However, little is known about the rhizosphere bacterial communities of moso bamboo in Cd/Pb contaminated soils. Therefore, this study investigated the assembly patterns and key taxa of rhizosphere bacterial communities of moso bamboo in Cd/Pb polluted and unpolluted soils, by field sampling, chemical analysis, and 16S rRNA gene sequencing. The results indicated α-diversity between Cd/Pb polluted and unpolluted soils showed a similar pattern (p > 0.05), while β-diversity was significantly different (p < 0.05). The relative abundance analysis indicated α-proteobacteria (37%) and actinobacteria (31%) were dominant in Cd/Pb polluted soils, while γ-proteobacteria (40%) and α-proteobacteria (22%) were dominant in unpolluted soils. Co-occurrence network analysis indicated microbial networks were less complex and more negative in polluted soils than in unpolluted soils. Mantel analysis indicated soil available phosphorus, organic matter, and available Pb were the most important environmental factors affecting microbial community structure. Correlation analysis showed 11 bacterial genera were significantly positively related to Cd/Pb. Overall, this study identified the bacterial community composition of bamboo rhizosphere in responding to Cd/Pb contamination and provides a theoretical basis for microbe-assistant phytoremediation in the future.

Study on the accelerated biodegradation of PAHs in subsurface soil via coupled low-temperature thermally treatment and electron acceptor stimulation based on metagenomic sequencing

In situ anoxic bioremediation is a sustainable technology to remediate PAHs contaminated soils. However, the limited degradation rate of PAHs under anoxic conditions has become the primary bottleneck hindering the application of this technology. In this study, coupled low-temperature thermally treatment (<50 °C) and EA biostimulation was used to enhance PAH removal. Anoxic biodegradation of PAHs in soil was explored in microcosms in the absence and presence of added EAs at 3 temperatures (15 °C, 30 °C, and 45 °C). The influence of temperature, EA, and their interaction on the removal of PAHs were identified. A PAH degradation model based on PLSR analysis identified the importance and the positive/negative role of parameters on PAH removal. Soil archaeal and bacterial communities showed similar succession patterns, the impact of temperature was greater than that of EA. Soil microbial community and function were more influenced by temperature than EAs. Close and frequent interactions were observed among soil bacteria, archaea, PAH-degrading genes and methanogenic genes. A total of 15 bacterial OTUs, 1 PAH-degrading gene and 2 methanogenic genes were identified as keystones in the network. Coupled low-temperature thermally treatment and EA stimulation resulted in higher PAH removal efficiencies than EA stimulation alone and low-temperature thermally treatment alone.

Environmental processes and health implications potentially mediated by dust-borne bacteria

Understanding microbial migration and survival mechanisms in dust events (DEs) can elucidate genetic and metabolic exchange between environments and help predict the atmospheric pathways of ecological and health-related microbial stressors. Dust-borne microbial communities have been previously characterized, but the impact and interactions between potentially active bacteria within transported communities remain limited. Here, we analysed samples collected during DEs in Israel, using amplicon sequencing of the 16S rRNA genes and transcripts. Different air trajectories and wind speeds were associated not only with the genomic microbial community composition variations but also with specific 16S rRNA bacterial transcripts. Potentially active dust-borne bacteria exhibited positive interactions, including carbon and nitrogen cycling, biotransformation of heavy metals, degradation of organic compounds, biofilm formation, and the presence of pathogenic taxa. This study provides insights into the potential interactive relationships and survival strategies of microorganisms within the extreme dust environment.

Core taxa, co-occurrence pattern, diversity, and metabolic pathways contributing to robust anaerobic biodegradation of chlorophenol

It is hard to achieve robustness in anaerobic biodegradation of trichlorophenol (TCP). We hypothesized that specific combinations of environmental factors determine phylogenetic diversity and play important roles in the decomposition and stability of TCP-biodegrading bacteria. The anaerobic bioreactor was operated at 35 °C (H condition) or 30 °C (L condition) and mainly fed with TCP (from 28 μM to 180 μM) and organic material. Metagenome sequencing was combined with 16S rRNA gene amplicon sequencing for the microbial community analysis. The results exhibited that the property of robustness occurred in specific conditions. The corresponding co-occurrence and diversity patterns suggest high collectivization, degree and evenness for robust communities. Two types of core functional taxa were recognized: dechlorinators (unclassified Anaerolineae, Thermanaerothrix and Desulfovibrio) and ring-opening members (unclassified Proteobacteria, Methanosarcina, Methanoperedens, and Rubrobacter). The deterministic process of the expansion of niche of syntrophic bacteria at higher temperatures was confirmed. The reductive and hydrolytic dechlorination mechanisms jointly lead to C-Cl bond cleavage. H ultimately adapted to the stress of high TCP loading, with more abundant ring-opening enzyme (EC 3.1.1.45, ∼55%) and hydrolytic dechlorinase (EC 3.8.1.5, 26.5%) genes than L (∼47%, 10.5%). The functional structure (based on KEGG) in H was highly stable despite the high loading of TCP (up to 60 μM), but not in L. Furthermore, an unknown taxon with multiple functions (dechlorinating and ring-opening) was found based on genetic sequencing; its functional contribution of EC 3.8.1.5 in H (26.5%) was higher than that in L (10.5%), and it possessed a new metabolic pathway for biodegradation of halogenated aromatic compounds. This new finding is supplementary to the robust mechanisms underlying organic chlorine biodegradation, which can be used to support the engineering, regulation, and design of synthetic microbiomes.

Microalgae mediated bioremediation of polycyclic aromatic hydrocarbons: Strategies, advancement and regulations

Polycyclic aromatic hydrocarbons (PAHs) are pervasive in the atmosphere and are one of the emerging pollutants that cause harmful effects in living systems. There are some natural and anthropogenic sources that can produce PAHs in an uncontrolled way. Several health hazards associated with PAHs like abnormality in the reproductive system, endocrine system as well as immune system have been explained. The mutagenic or carcinogenic effects of hydrocarbons in living systems including algae, vertebrates and invertebrates have been discussed. For controlling PAHs, biodegradation has been suggested as an effective and eco-friendly process. Microalgae-based biosorption and biodegradation resulted in the removal of toxic contaminants. Microalgae both in unialgal form and in consortium (with bacteria or fungi) performed good results in bioaccumulation and biodegradation. In the present review, we highlighted the general information about the PAHs, conventional versus advanced technology for removal. In addition microalgae based removal and toxicity is discussed. Furthermore this work provides an idea on modern scientific applications like genetic and metabolic engineering, nanomaterials-based technologies, artificial neural network (ANN), machine learning (ML) etc. As rapid and effective methods for bioremediation of PAHs. With several pros and cons, biological treatments using microalgae are found to be better for PAH removal than any other conventional technologies.

Improved sea rice yield and accelerated di-2-ethylhexyl phthalate (DEHP) degradation by straw carbonization returning in coastal saline soils

Di-2-ethylhexyl phthalate, a persistent organic contaminant, is widely distributed in the environment and poses substantial threats to human health; however, there have been few investigations regarding the risks and remediation of DEHP in coastal saline soils. In this work, we studied the influences of straw carbonization returning on sea rice yield and DEHP degradation. Straw carbonization returning significantly increased soil nutrients and reduced salt stress to improve sea rice yield. DEHP degradation efficiency was enhanced to a maximum of 78.27% in straw carbonized return with 60% sea rice, mainly attributed to the high pH value, high soil organic matter and enriched potential DEHP degraders of Nocardioides, Mycobacterium and Bradyrhizobium. Some key genes related to metabolism (esterase and cytochrome P450) and DEHP-degradation (pht4, pht5, pcaG, dmpB, catA and fadA) were elevated and explained the accelerated DEHP degradation, shifting from the benzoic acid pathway to the protocatechuate pathway in straw carbonization returning. The results obtained in this study provide a deep and comprehensive understanding of sea rice yield improvement and DEHP degradation mechanisms in coastal paddy soil by a straw carbonization returning strategy.

Exploring the role of microbes for the management of persistent organic pollutants

Persistent organic pollutants (POPs) are chemicals which have been persisting in the environment for many years due to their longer half-lives. POPs have gained attention over the last few decades due to the unsustainable management of chemicals which led to their widespread and massive contamination of biota from different strata and environments. Due to the widespread distribution, bio-accumulation and toxic behavior, POPs have become a risk for organisms and environment. Therefore, a focus is required to eliminate these chemicals from the environment or transform into non-toxic forms. Among the available techniques for the removal of POPs, most of them are inefficient or incur high operational costs. As an alternative to this, microbial bioremediation of POPs such as pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, pharmaceuticals and personal care products is much more efficient and cost-effective. Additionally, bacteria play a vital role in the biotransformation and solubilization of POPs, which reduces their toxicity. This review specifies the Stockholm Convention that evaluates the risk profile for the management of existing as well as emerging POPs. The sources, types and persistence of POPs along with the comparison of conventional elimination and bioremediation methods of POPs are discussed comprehensively. This study demonstrates the existing bioremediation techniques of POPs and summaries the potential of microbes which serve as enhanced, cost-effective, and eco-friendly approach for POPs elimination.

Skin microbiome differentiates into distinct cutotypes with unique metabolic functions upon exposure to polycyclic aromatic hydrocarbons

BACKGROUND

The effects of air pollutants, particularly polycyclic aromatic hydrocarbons (PAHs), on the skin microbiome remain poorly understood. Thus, to better understand the interplay between air pollutants, microbiomes, and skin conditions, we applied metagenomics and metabolomics to analyze the effects of PAHs in air pollution on the skin microbiomes of over 120 subjects residing in two cities in China with different levels of air pollution.

RESULTS

The skin microbiomes differentiated into two cutotypes (termed 1 and 2) with distinct taxonomic, functional, resistome, and metabolite compositions as well as skin phenotypes that transcended geography and host factors. High PAH exposure was linked to dry skin and cutotype 2, which was enriched with species with potential biodegradation functions and had reduced correlation network structure integrity. The positive correlations identified between dominant taxa, key functional genes, and metabolites in the arginine biosynthesis pathway in cutotype 1 suggest that arginine from bacteria contributes to the synthesis of filaggrin-derived natural moisturizing factors (NMFs), which provide hydration for the skin, and could explain the normal skin phenotype observed. In contrast, no correlation with the arginine biosynthesis pathway was observed in cutotype 2, which indicates the limited hydration functions of NMFs and explains the observed dry skin phenotype. In addition to dryness, skin associated with cutotype 2 appeared prone to other adverse conditions such as inflammation.

CONCLUSIONS

This study revealed the roles of PAHs in driving skin microbiome differentiation into cutotypes that vary extensively in taxonomy and metabolic functions and may subsequently lead to variations in skin-microbe interactions that affect host skin health. An improved understanding of the roles of microbiomes on skin exposed to air pollutants can aid the development of strategies that harness microbes to prevent undesirable skin conditions. Video Abstract.

Removal of cadmium and polychlorinated biphenyls by clover and the associated microbial community in a long-term co-contaminated soil

Legumes such as clover are cost-effective and environmentally friendly components of strategies for remediating soils contaminated with heavy metals or organic pollutants. However, the mechanisms by which clover remediates co-contaminated soils are unclear. The present study explored the effects of phytoremediation by clover on pollutant removal and the microbial community in soil co-contaminated with cadmium (Cd) and polychlorinated biphenyls (PCBs). After 18 months of phytoremediation, Cd removal increased from 20.25 % in the control to 40.65 % in soil planted with clover, while PCB removal increased from 29.81 % to 60.02 %. High-throughput sequencing analysis showed that the relative abundances of the bacterial phylum Proteobacteria and the diazotrophic genus Rhizobium increased significantly after phytoremediation. Random forest analysis showed that bacterial and diazotrophic diversity significantly influenced Cd and PCB removal. Furthermore, co-occurrence network and correlation analyses revealed that Rhizobiales and Micromonosporales were the main bacteria associated with Cd removal, while Rhizobiales, Burkholderiales, and Xanthomonadales were identified as the main degraders of PCBs. PICRUSt functional prediction demonstrated that the gene bphC, which is related to PCB degradation, was significantly increased in the rhizosphere soil in the presence of clover. These results provide a better understanding for further studies of remediation efficiency by clover, rhizosphere microbial response and remediation mechanisms of co-contaminated soils under in situ conditions in the field.

Enhancement of nitrogen fixation and diazotrophs by long-term polychlorinated biphenyl contamination in paddy soil

Biological nitrogen fixation (BNF) driven by diazotrophs is a major means of increasing available nitrogen (N) in paddy soil, in addition to anthropogenic fertilization. However, the influence of long-term polychlorinated biphenyl (PCB) contamination on the diazotrophic community and nitrogen fixation in paddy soil is poorly understood. In this study, samples were collected from paddy soil subjected to > 30 years of PCB contamination, and the soil diazotrophic community and N₂ fixation rate were evaluated by Illumina MiSeq sequencing and acetylene reduction assays, respectively. The results indicated that high PCB contamination increased diazotrophic abundance and the N₂ fixation rate, and altered diazotrophic community structure in the paddy soil. The random forest model demonstrated that the β-diversity of the diazotrophic community was the most significant predictor of the N₂ fixation rate. Structure equation modeling identified a specialized keystone diazotrophic ecological cluster, predominated by Bradyrhizobium, Desulfomonile, and Cyanobacteria, as the key driver of N₂ fixation. Overall, our findings indicated that long-term PCB contamination enhanced the N₂ fixation rate by altering diazotrophic community abundance and structure, which may deepen our understanding of the ecological function of diazotrophs in organic-contaminated soil.

Occurrence of OCPs & PCBs and their effects on multitrophic biological communities in riparian groundwater of the Beiluo River, China

Persistent Organic Pollutants (POPs) may exert adverse effects on human and ecosystem health. However, as an ecologically fragile zone with strong interaction between river and groundwater, the POPs pollution in the riparian zone has received little attention. The goal of this research is to examine the concentrations, spatial distribution, potential ecological risks, and biological effects of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the riparian groundwater of the Beiluo River, China. The results showed that the pollution level and ecological risk of OCPs in riparian groundwater of the Beiluo River were higher than PCBs. The presence of PCBs (Penta-CBs, Hexa-CBs) and CHLs, respectively, may have reduced the richness of bacteria (Firmicutes) and fungi (Ascomycota). Furthermore, the richness and Shannon's diversity index of algae (Chrysophyceae and Bacillariophyta) decreased, which could be linked to the presence of OCPs (DDTs, CHLs, DRINs), and PCBs (Penta-CBs, Hepta-CBs), while for metazoans (Arthropoda) the tendency was reversed, presumably as a result of SULPHs pollution. In the network analysis, core species belonging to bacteria (Proteobacteria), fungi (Ascomycota), and algae (Bacillariophyta) played essential roles in maintaining community function. Burkholderiaceae and Bradyrhizobium can be considered biological indicators of PCBs pollution in the Beiluo River. Note that the core species of interaction network, playing a fundamental role in community interactions, are strongly affected by POPs pollutants. This work provides insights into the functions of multitrophic biological communities in maintaining the stability of riparian ecosystems through the response of core species to riparian groundwater POPs contamination.

In silico prediction of potential indigenous microbial biomarkers in Penaeus vannamei identified through meta-analysis and genome-scale metabolic modelling

BACKGROUND

Understanding the microbiome is crucial as it contributes to the metabolic health of the host and, upon dysbiosis, may influence disease development. With the recent surge in high-throughput sequencing technology, the availability of microbial genomic data has increased dramatically. Amplicon sequence-based analyses majorly profile microbial abundance and determine taxonomic markers. Furthermore, the availability of genome sequences for various microbial organisms has prompted the integration of genome-scale metabolic modelling that provides insights into the metabolic interactions influencing host health. However, the analysis from a single study may not be consistent, necessitating a meta-analysis.

RESULTS

We conducted a meta-analysis and integrated with constraint-based metabolic modelling approach, focusing on the microbiome of pacific white shrimp Penaeus vannamei, an extensively cultured marine candidate species. Meta-analysis revealed that Acinetobacter and Alteromonas are significant indicators of "health" and "disease" specific taxonomic biomarkers, respectively. Further, we enumerated metabolic interactions among the taxonomic biomarkers by applying a constraint-based approach to the community metabolic models (4416 pairs). Under different nutrient environments, a constraint-based flux simulation identified five beneficial species: Acinetobacter spWCHA55, Acinetobacter tandoii SE63, Bifidobacterium pseudolongum 49 D6, Brevundimonas pondensis LVF1, and Lutibacter profundi LP1 mediating parasitic interactions majorly under sucrose environment in the pairwise community. The study also reports the healthy biomarkers that can co-exist and have functionally dependent relationships to maintain a healthy state in the host.

CONCLUSIONS

Toward this, we collected and re-analysed the amplicon sequence data of P. vannamei (encompassing 117 healthy and 142 disease datasets). By capturing the taxonomic biomarkers and modelling the metabolic interaction between them, our study provides a valuable resource, a first-of-its-kind analysis in aquaculture scenario toward a sustainable shrimp farming.

Potential Utilization of Bacterial Consortium of Symbionts Marine Sponges in Removing Polyaromatic Hydrocarbons and Heavy Metals, Review

Toxic materials in waste generally contain several components of the global trending pollutant category, especially PAHs and heavy metals. Bioremediation technology for waste management that utilizes microorganisms (bacteria) has not been fully capable of breaking down these toxic materials into simple and environmentally friendly chemical products. This review paper examines the potential application of a consortium of marine sponge symbionts with high performance and efficiency in removing PAHs and heavy metal contaminants. The method was carried out through a review of several related research articles by the author and published by other researchers. The results of the study conclude that the development of global trending pollutant (GTP) bioremediation technology could be carried out to increase the efficiency of remediation. Several types of marine sponge symbiont bacteria, hydrocarbonoclastic (R-1), metalloclastic (R-2), and metallo-hydro-carbonoclastic (R-3), have the potential to be applied to improve waste removal performance. A consortium of crystalline bacterial preparations is required to mobilize into GTP-exposed sites rapidly. Bacterial symbionts of marine sponges can be traced mainly to sea sponges, whose body surface is covered with mucus.

Metal-free catalysis for organic micropollutant degradation in waste activated sludge via poly(3-hydroxybutyrate) biopolymers using Cupriavidus sp. L7L coupled with peroxymonosulfate

This study employed a novel and environment-friendly biopolymer/oxidant catalytic system, viz., poly(3-hydroxybutyrate)/peroxymonosulfate (PHB/PMS), for pretreating wastewater sludge for the first time. Under optimal conditions, i.e., 3.1 × 10^-4 M of PMS and 3.3 g/L of PHB at pH = 6.0, the PAHs in the sludge matrix was decreased by 79 % in 12 h. Increase in salinity (75 % synthetic seawater) achieved 83 % of PAHs degradation. Functional groups (CO) of the biopolymer matrix were active centers for biopolymer-mediated electron transfer that produced reactive oxygen species (SO₄^-, HO, and ¹O₂) for adsorption and catalytic oxidation of PAHs in the sludge. Functional metagenomic analysis revealed the main genus, Conexibacter (phylum, Actinobacteria) exhibited PAH-degrading function with high efficiency in the biodegradation of PAHs from sludge pretreated with PHB/PMS. Coupling chemical oxidation and biostimulation using bacterial polymer-based biomaterials is effective and beneficial for pretreating wastewater sludge toward circular bioeconomy.

PCB-77 biodegradation potential of biosurfactant producing bacterial isolates recovered from contaminated soil

Polychlorinated biphenyls (PCBs) are persistent organic pollutants widely distributed in the environment and possess deleterious health effects. The main objective of the study was to obtain bacterial isolates from PCB-contaminated soil for enhanced biodegradation of PCB-77. Selective enrichment resulted in the isolation of 33 strains of PCB-contaminated soil nearby Bhilai steel plant, Chhattisgarh, India. Based on the prominent growth using biphenyl as the sole carbon source and the confirmation of its degradation by GC-MS/MS analysis, four isolates were selected for further study. The isolates identified by 16S rRNA gene sequencing were Pseudomonas aeruginosa MAPB-2, Pseudomonas plecoglossicida MAPB-6, Brucella anthropi MAPB-9, and Priestia megaterium MAPB-27. The isolate MAPB-9 showed a degradation of 66.15% biphenyl, while MAPB-2, MAPB-6, and MAPB-27 showed a degradation of 62.06, 57.02, and 56.55%, respectively in 48 h. Additionally, the degradation ability of these strains was enhanced with addition of co-metabolite glucose (0.2%) in the culture medium. Addition of glucose showed 100% degradation of biphenyl by MAPB-9, in 48 h, while MAPB-6, MAPB-2, and MAPB-27 showed 97.1, 67.5, and 53.3% degradation, respectively as analyzed by GC-MS/MS. Furthermore, in the presence of inducer, PCB-77 was found to be 59.89, 30.49, 27.19, and 4.43% degraded by MAPB-6, MAPB-9, MAPB-2, and MAPB-27, respectively in 7 d. The production of biosurfactants that aid in biodegradation process were observed in all the isolates. This was confirmed by ATR-FTIR analysis that showed the presence of major functional groups (CH₂, CH₃, CH, = CH₂, C–O–C, C-O) of the biosurfactant. The biosurfactants were further identified by HPTLC and GC-MS/MS analysis. Present study is the first to report PCB-77 degradation potential of Pseudomonas aeruginosa, B. anthropi, Pseudomonas plecoglossicida, and Priestia megaterium. Similarly, this is the first report on Pseudomonas plecoglossicida and Priestia megaterium for PCB biodegradation. Our results suggest that the above isolates can be used for the biodegradation of biphenyl and PCB-77 in PCB-contaminated soil.