Whole Genome Shotgun Sequencing-Based Insights into the Benzene and Xylene Degrading Potentials of Bacteria

Due to their hazardous effects on human health and air quality, benzene and xylene constitute the primary pollutants. Coupling the physicochemical strategies with bacterial bioremediation is an emerging mode of decontamination. Considering the limited understanding of benzene and xylene degradation pathways in the genus Bacillus, failure of earlier documented bacteria to degrade these compounds due to poor optimization and complicated real-world contamination scenarios, we initiated the current project. It is an attempt to explore the gene repertoire and pathways associated with the bioremediation of benzene and xylene in new and efficient bacteria. Eleven bacteria were isolated from tannery industry soil in a previous study. Bacterial DNA was extracted by the organic method. To prepare a sample for whole genome sequencing (WGS) analysis, a mixture of genomic DNA was made by adding DNA from each isolate in equimolar concentration (100 ng). The sample was subjected to WGS. Results obtained as FASTq files were submitted to Sequence Read Archives (SRA), NCBI, to get the accession number assigned. Taxonomic profiling revealed that the sample was composed of phyla Proteobacteria (76%), Firmicutes (16%) and unclassified phyla (8%). Functional annotation unraveled the presence of benzoate, m-, p- and o-xylene isomers, benzene, aminobenzoate, 2-, 3- and 4-fluorobenzoate, toluene, chloroalkane and chloroalkene, naphthalene, polycyclic aromatic hydrocarbons (PAHs), dioxin, caprolactum, atrazine, styrene, and chlorobenzene and chlorocyclohexane degradation enzymes and pathways. It is the first ever study documenting the benzene degradation pathway similar to Gram-negative bacteria, in the genus Bacillus, inhabiting the tannery soil and coexistence of metabolic pathways for multiple organic pollutants.