Heavy metal pollution assessment and bioremediation potential of multidrug-resistant Proteus mirabilis isolated from Buckingham canal, Chennai.

Abstract

The present study investigates the physicochemical, heavy metal, and microbiological characteristics of water and sediment samples from the Buckingham Canal, Chennai, to assess environmental pollution and explore the bioremediation potential of native bacterial isolates. The water and sediment samples revealed the concentration of heavy metals in the sequence Zn > Mn > Pb > Cu > Cr and Zn > Mn > Cu > Cr > Pb. Among 25 isolates, BCSS04 showed exceptional resistance, tolerating up to 2100 ppm (Pb), 1900 ppm (Zn, Mn, and Cr), and 1300 ppm (Cu), identified as Proteus mirabilis through 16S rRNA sequencing (GenBank accession: PP980976.1). Molecular analysis confirmed the presence of the pbrA gene, while antibiotic susceptibility profiling revealed multidrug resistance, suggesting potential co-selection of metal and antibiotic resistance traits. Growth profiling under metal-induced stress revealed the highest bacterial growth under Mn (0.654 to 0.996) and Pb (0.623 to 0.984). Uptake studies confirmed efficient biosorption capabilities, with peak Pb and Zn uptake reaching 4.23 and 4.21 mg/g, respectively, at 100 ppm. Bioaccumulation assays supported these findings, with maximum accumulation rates for Zn (69.67%) and Pb (67.11%) at 100 ppm, gradually decreasing with increasing concentrations due to saturation or stress effects. SEM and FTIR analyses demonstrated structural and biochemical changes in Proteus mirabilis under metal stress. Molecular docking further revealed strong interactions between heavy metals against Metallothionein SmtA exhibited the strongest interaction with Zn (binding energy: -9.8 kcal/mol), involving eight active residues (TYR A:18, GLY A:53, ASP A:73, ASP A:50, GLU A:55, ARG A:26, HIS A:119, GLY A:52). The integrated physiological, biochemical, and molecular insights affirm the potential of Proteus mirabilis as a promising candidate for bioremediation of heavy metal-contaminated environments.