Metagenomic exploration of indigenous bacteria with their bioaugmentation for enhanced phytobial remediation of tannery effluent with Lemna minor

Despite the toxic and persistent nature of tannery effluent (TE), limited research studies have evaluated Lemna minor-based phytobial remediation in real TE. The current study aimed at TE remediation using L. minor with the assistance of indigenous heavy metals (HMs) tolerant bacterial strains. Five coded TE indigenous bacterial strains (S1WC4, S2WC3, S2WC2, S3WC1 and S1WC2), isolated from TE samples were applied in combination with L. minor for treatment of TE dilutions (2%, 5%, 10% and 15%), while pond water (PW) treatments were used as a control. The bacterial community was also profiled through 16S rRNA metagenomic amplicon sequencing. Results showed that treatments aided by consortia demonstrated higher efficiencies for metal removal, i.e., Pb removal ∼80–95%, Cr removal ∼80–90%, Cu removal ∼55–83%, Cd removal ∼70–85%. The consortia treatments also enhanced bioaccumulation factors (e.g.,BAF up to 18.4 for Pb and 8.2 for Cr in 5% TE), with higher biomass and SPAD values compared to control treatments. The TE bacterial community was dominated by stress tolerant bacterial taxa, and the ecological importance of these taxa was evaluated with PICRUSt2-analysis, predicting pathways associated with community survival under HMs stress conditions. Biologically driven removal was confirmed in logistic modeling that showed time-dependent HMs removal. Results of the study, therefore, conclude that bioaugmentation had a significant effect on the performance of the remediation system when compared with control treatments (plant-only treatments).