Metagenomic insights into bacterial communities’ structures in polycyclic aromatic hydrocarbons degrading consortia

Abstract

Assembly of bacterial communities under xenobiotic stress, such as in the presence of various PAHs and their metabolic activities in form of consortia, are less studied. Eight bacterial consortia were developed from PAHs-contaminated sediments in minimal media, using various combinations of naphthalene, phenanthrene, fluoranthene and pyrene. Among eight, competency of consortium ACDMRT-8 was notable, it showed 88.5%, 85.8%, 58.0% and 60.3% degradation of naphthalene, phenanthrene, fluoranthene and pyrene (concentration of total-PAHs 800 ppm, each PAH 200 ppm) within 9 d at room temperature, respectively. After 40 enrichment cycles, bacterial communities were characterized using high-throughput 16S rRNA gene amplicon sequencing of all eight consortia. Though bacterial communities in all consortia were pre-dominated by Proteobacteria, individual diversity varied depending upon enrichment conditions and combinations of PAHs provided. Pseudomonas sp. were abundant in four consortia, which favored all-four PAHs degradation. Bordetella, Chelatococcus and Azoarcus were abundantly found in other consortia with changes in temperature and PAHs. The radical changes in bacterial community at genus level were well reflected in beta-diversity analysis, where four consortia were clustered together, while another group contained three consortia and single consortium remained separated from other two clusters. Dissimilarity analysis using SIMPER suggested that Pseudomonas, Azoarcus, Bordetella, Chelatococcus and Chelativorans formed top 5 abundant genera within eight consortia enriched for PAH biodegradation. Molecular ecological network amongst dominant 17 genera from eight consortia was constructed. The functional competence in form of hydrocarbon degrading genes and pathways were predicted using PICRUSt2 tool and has indicated abundance of ortho-cleavage over meta-cleavage pathways.