Industrial effluent-derived Acinetobacter sp. PbS1A2 as a bioremediator against lead toxicity in Labeo rohita

ABSTRACT Lead pollution is recognized as a major global environmental problem that poses a serious threat to ecological integrity and environmental sustainability. The current study shows the bioremedial potential of Pb-resistant Acinetobacter sp. PbS1A2 in Labeo rohita . The fish were divided into three experimental treatments, namely, Control (T 0 ), Pb only (T 1 ), and Pb + Acinetobacter sp. (T 2 ). The treatment T 2 was particularly exposed to a concentration of 1.5 × 10 8 CFU/mL of Acinetobacter sp. along with Pb (1 mg L −1 ) for a period of 30 days. The results revealed that Acinetobacter sp. PbS1A2 could tolerate Pb concentrations up to 30 mM, along with resistance to other heavy metal ions. Pb exposure significantly increased the activity of all antioxidant enzymes, with glutathione transferase exhibiting the greatest increase (795%), followed by peroxidase (229%), superoxide dismutase (195%), catalase (104%), and ascorbate peroxidase (28%). Furthermore, Fourier transform infrared spectroscopy was employed to identify the functional groups involved in Pb biosorption, while intracellular accumulation was confirmed via energy dispersive X-ray and scanning electron microscopy analyses. At the end of the 1-month trial, fish in the T 2 group treated with Acinetobacter sp. exhibited a significantly higher survival rate, improved growth performance, better body composition, and increased amylase and protease activities than those in the T 1 group. Furthermore, the T 2 treatment mitigated the negative impacts of Pb on hematological and biochemical parameters and restored histological damage in the fish organs. The current study suggests that Acinetobacter sp., due to its heavy metal tolerance, could effectively ameliorate Pb bioavailability in aquatic habitats and enhance environmental health. IMPORTANCE The continuously rising Pb discharge in aquatic ecosystems, particularly in the industrial regions of South Asia, jeopardizes ecological integrity and the health of economically crucial fish such as Labeo rohita , consequently affecting food security. Conventional remediation techniques are often expensive, energy-intensive, and pose ecological risks. This study addresses a significant gap by presenting a thorough bioremediation process encompassing the isolation and characterization of a newly identified multi-metal-resistant Acinetobacter sp. (PbS1A2) from industrial wastewater, which facilitates in vivo recovery in Labeo rohita contaminated with Pb. Isolated from a contaminated site, Acinetobacter sp. have evolved natural metal-resistant mechanisms under environmental stress, resulting in better remediation than lab-engineered options. This is distinguished from studies that solely address the in vitro efficiencies of Pb removal. The research offers extensive biological evidence indicating that Pb-induced damage can be effectively mitigated. The results concerning growth performance, hematological assessments, digestive enzyme activities, tissue accumulation, and histopathological evaluations suggest an economical, expandable, and scientifically validated approach to manage Pb pollution in aquatic ecosystems.