A silver lining in the Sea: Molecular insight and analytical validation of marine bacteria in lead bioremediation

The accumulation of lead (Pb²⁺) in marine ecosystems can disrupt microbial diversity, alter essential biochemical processes, and negatively affect the overall health of the marine food web. Such changes in microbial communities can reduce nutrient cycling efficiency, impacting higher organisms and posing risks to human health through seafood consumption. Marine bacteria have the potential to mitigate Pb²⁺ contamination and change harmful heavy metal ions into less harmful substances. In this study, six Pb²⁺ resistance bacteria from South Andaman have been selected that have been grown in a wide range of lead nitrate Pb(NO₃)₂ concentrations, i.e., 0 mM to 3.01 mM, and insight into their mechanism of Pb²⁺ detoxification. The molecular characterization revealed that all the bacterial strains belonged to the genus Bacillus . The presence of the pbrA gene, which encodes for Pb²⁺ efflux mechanism, was amplified in NIOT_PRB35. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis confirmed that NIOT_PRB247 showed the maximum 83.71±1.33% removal of Pb²⁺ ions. Changes in functional groups (OH, N-H, -CH₂) and hydrogen-bonding energy (ranging from 17.25 kJ·mol⁻¹ to 10.80 kJ·mol⁻¹) provide insight into the strong and weak interactions of Pb²⁺ ions with functional groups, effectively reducing their bioavailability and toxicity. The X-ray Diffraction (XRD) analysis confirmed Pb²⁺ bioprecipitation in NIOT_PRB35 and NIOT_PRB247 as lead phosphate hydroxide Pb 10 (PO 4 ) 6 (OH) 2 , with average crystallite sizes averaging 1.135 nm and Dislocation Density approximately 0.76 × 10¹⁸ m⁻². The findings indicate that marine bacteria are effective biosorbents for removing Pb²⁺ and could be utilized in marine and terrestrial bioremediation efforts.