## 2 Materials and Methods
### Extraction of Metabolites in Contaminated Soils (Field)
#### 2.2.2 Bacterial Community Identification (Field)  
The method of 16s rRNA sequencing was nearly the same as the previous research of the authors [12]. The soil sample was collected at Gimpo, in Gyeonggi Province, South Korea, where the toluene fire accident actually occurred in 2016. The soils were collected each 100 meters apart from the site of the accident along the diffusion direction of the gas cloud when the chemical accident occurred. The collected soils were screened with a 10-mesh sieve (2 mm diameter) and mixed homogeneously. The microbial communities in soil were first extracted using a PowerSoil DNA Extraction Kit (Mobio Laboratories, USA). All soil samples were sieved to remove stones and leaves. The QC (Quality Control) analyses of the DNA of all samples were performed using NanoDrop ND-8000 (Thermo Fisher Scientific Inc., Waltham, MA, USA). The bacterial primer sets used included 341F (5\({}^{\prime}\)CCTACGGGNGGCG\(\mathrm{WGCAG}\)\(3^{\prime}\)) and 805 Rmod (5\({}^{\prime}\) GACTACNVGGGTWTCTAATCC\(\mathrm{3}^{\prime}\)). The total metagenomic DNA was subjected to PCR amplification by targeting a 460 bp fragment of the 165 rRNA regions V3-V4. For PCR amplification, an initial denaturation was performed for 3 min at 95 \({}^{\circ}\)C, followed by annealing at 95 \({}^{\circ}\)C for 30 s, primer annealing at 55 \({}^{\circ}\)C for 30 s, extended annealing at 72 \({}^{\circ}\)C for 30 s and final annealing at 72 \({}^{\circ}\)C for 5 min. The PCR products were identified using 1% agarose gel electric shock visualized under the Gel Doc System (BioRad, Hercules, CA, USA). After correcting amplified organisms with CleanPCR (CleanNA), the purified products of equal concentration were collected and put together, and then short fragments (non-targeted products) were removed using CleanPCR (CleanNR). A DNA 7500 chip was used with the Bioanalyzer 2100 (Agilent, Santa Clara, CA, USA) to evaluate the quality and size of products. Sequencing was performed using the Illumina MiSeq Sequencing System (Illumina, Diego, CA, USA) in Chunlab, Inc (Seoul, Korea). The MiSeq pipeline method is based on the EzBioCloud database. Raw read processing started with Trimomatic 0.321 for quality inspection and filtering low quality (<Q25). After the QC pass, two-way sequence data were merged using PANDAseq2. The trim primer was reduced to a similarity of 0.8 using ChunLab's program. Reduced-noise sequences used DUDE-Seq4, and non-replicated reads were extracted by UCLUST5. The EzBioCloud database was used for taxonomic allocation using USEARCH (8.1861_i86 linux32) 5 and more accurate pairwise alignment 6. Readings not identified as species level (<97% similarity) were compiled in the EzBioCloud database, and UCLUST5 and CDHIT8 were used to perform de novo clustering to create additional operational taxonomic units (OTUs). Finally, any OTU with a single read (single tone) was omitted from further analysis, while alpha diversity index 8-13, lean curve 14, and ranking rich curve 15 were estimated using an internal code. EzBioCloud was used to determine the microbial community composition of each sample and Krona.