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This study investigated the role of an allochthonous Gram-positive wastewater bacterium (Bacillus sp. KUJM2) selected through rigorous screening, for the removal of potentially toxic elements (PTEs; As, Cd, Cu, Ni) and promotion of plant growth under PTE-stress conditions. The dried biomass of the bacterial strain removed PTEs (5 mg L−1) from water by 90.17–94.75 and 60.4–81.41%, whereas live cells removed 87.15–91.69 and 57.5–78.8%, respectively, under single-PTE and co-contaminated conditions. When subjected to a single PTE, the bacterial production of indole-3-acetic acid (IAA) reached the maxima with Cu (67.66%) and Ni (64.33%), but Cd showed an inhibitory effect beyond 5 mg L−1 level. The multiple-PTE treatment induced IAA production only up to 5 mg L−1 beyond which inhibition ensued. Enhanced germination rate, germination index and seed production of lentil plant (Lens culinaris) under the bacterial inoculation indicated the plant growth promotion potential of the microbial strain. Lentil plants, as a result of bacterial inoculation, responded with higher shoot length (7.1–27.61%), shoot dry weight (18.22–36.3%) and seed production (19.23–29.17%) under PTE-stress conditions. The PTE uptake in lentil shoots decreased by 67.02–79.85% and 65.94–78.08%, respectively, under single- and multiple-PTE contaminated conditions. Similarly, PTE uptake was reduced in seeds up to 72.82–86.62% and 68.68–85.94%, respectively. The bacteria-mediated inhibition of PTE translocation in lentil plant was confirmed from the translocation factor of the respective PTEs. Thus, the selected bacterium (Bacillus sp. KUJM2) offered considerable potential as a PTE remediating agent, plant growth promoter and regulator of PTE translocation curtailing environmental and human health risks. Image 1 • Dried/live metal(loid)-resistant Bacillus sp. acts as agent of toxicants' removal. • Synthesizes IAA in contaminated state (single and multiple) and induces plant growth. • Modulation of translocation/retention lowered toxicant levels in plant parts. • Toxicant level in edible part (seed) lied within permissible limits averting risk. • Biomass cuts soil toxic load to harness remedial and agronomic double dividends. [ABSTRACT FROM AUTHOR]

In this study the multiple metal(loid) (As, Cd, Cu and Ni) resistant bacterium Serratia sp. KUJM3 was able to grow in both single and multiple metal(loid) contaminated wastewater and removed them by 34.93–48.80% and 22.93–32%, respectively. It reduced As(v) to As(III) by 68.44–85.06% in a concentration dependent manner. The strain's IAA production potential increased significantly under both metal(loid)s regime. The lentil (Lens culinaris) seed germination and seed production were enhanced with the exogenous bacterial inoculation by 20.39 and 16.43%, respectively. Under both multi-metal(loid) regimes the bacterial inoculation promoted shoot length (22.65–51.34%), shoot dry weight (33.89–66.11%) and seed production (13.46–35%). Under bacterial manipulation the metal(loid)s immobilization increased with concomitant curtailment of translocation in lentil plant by 61.89–75.14% and 59.19–71.14% in shoot and seed, respectively. The strain biomineralized struvite (MgNH 4 PO 4 ·6H 2 O) from human urine @ 403 ± 6.24 mg L−1. The fertilizer potential of struvite was confirmed with the promotion of cowpea (Vigna unguiculata) growth traits e.g. leaf number (37.04%), pod number (234%), plant wet weight (65.47%) and seed number (134.52%). Thus Serratia sp. KUJM3 offers multiple benefits of metal(loid)s bioremediation, As(V) reduction, plant growth promotion, and struvite biomineralization garnering a suite of appealing environmental applications. [ABSTRACT FROM AUTHOR]