Assessment into the cadmium and lead ion biosorption capabilities from halophilic bacteria from genus Brachybacterium

Cadmium (Cd) and lead (Pb) ions are highly toxic elements present in the water, soil and sediments of the Yucatan Peninsula. The use of Cd- and Pb-resistant microorganisms as natural biosorbents could be considered an innovative strategy for the bioremediation of ecosystems contaminated with these ions. In this investigation, halophilic bacteria of the genus Brachyobacterium were identified that were tolerant to high concentrations of metal ions isolated from the coasts of Isla Arena, Mexico. Sediment parameters showed pH values ​​ > 7.6 and < 8.5; temperatures > 30 °C and < 33 °C; salinity > 2.0% and < 4.2%; conductivity > 2411 µs/cm and < 8240 µs/cm; and total solids > 1204 ppm and < 4193 ppm. Isolates S1p and S1a were genetically identified as Brachybacterium paraconglomeratum and Brachybacterium saurashtrense, both with 99.7% identity, according to the software employed. The minimum inhibitory concentration (MIC) values ​​indicated a tolerance of 1656 mg/L of Pb for both strains; while for Cd, the tolerance values ​​were 591 mg/L and 236 mg/L for S1p and S1a, respectively. Additionally, FT-IR analysis demonstrated that, most likely the functional groups involved in this metal-bacteria interaction are OH-, NH-, and/or COOH-, associated with proteins, lipids and fatty acids in cell walls of bacteria, as also reported by other authors. In this study, we observed that, at a pH of 6.5 and a time of 48 h, a maximum biosorption capacity of 58 mg/L was obtained. This work presents the biosorption capacity of cadmium and leads ions from halophilic bacteria of the genus Brachybacterium isolated from undisturbed sites and opens the possibility of exploring this methodology in other scenarios.