Heavy Metal Tolerance of Microorganisms Isolated from Coastal Marine Sediments and Their Lead Removal Potential

In this study, 338 microorganisms, comprising 271 bacteria and 67 fungi, were isolated from sediment samples collected from underexplored Pacific and Caribbean regions of Colombia. Screening trials were conducted on selected strains (n = 276) to assess their tolerance to cadmium (Cd²⁺), lead (Pb²⁺), and zinc (Zn²⁺), leading to the identification of six bacteria capable of withstanding 750 mg·L^-1 of each heavy metal ion. Three promising microorganisms, identified as Enterobacter sp. INV PRT213, Pseudomonas sp. INV PRT215, and Stenotrophomonas sp. INV PRT216 were selected for lead removal experiments using LB broth medium supplemented with 400 mg·L^-1 Pb²⁺. Among these, Pseudomonas sp. INV PRT215 exhibited significant potential, removing 49% of initial Pb²⁺ after 240 min of exposure (16.7 g wet biomass·L^-1, pH 5, 30 °C). Infrared spectra of Pb-exposed biomass showed changes in functional groups, including carbonyl groups of amides, carboxylate, phosphate, hydroxyl, and amine groups, compared to the not-exposed control. These changes suggested interactions between the metal and functional groups in the biomass. The findings of this study highlight the potential of microorganisms derived from coastal marine environments as promising candidates for future applications in bioremediation of polluted environments contaminated with heavy metals.