Genomic and functional characterization of the novel marine bacterial isolate Lysinibacillus sphaericus PG22 highlights the potential for metalsbiomineralization via urease activity

Potentially toxic elements (PTEs) are cause of environmental concerns due to their accumulation and toxicity in marine and terrestrial environments. The crucial removal of these compounds has stimulated the development of many strategies, including biobased ones such as biomineralization. Microbial induced carbonate precipitation (MICP) is a biomineralization process that can form high amounts of calcium carbonate in a very short time. MICP is emerging as an eco-friendly strategy to mitigate PTEs pollution through the co-precipitation of metal(oid) carbonates. This study evaluates the MICP potential of Lysinibacillus sphaericus PG22, a marine gram-positive sporulating bacterium isolated from N-Tyrrhenian sediments. Genome analysis revealed the presence of urease and metal resistance genes, confirming its validated ability to tolerate 1600 ppm of Pb(NO₃)₂. We demonstrated PG22’s ureolytic activity, leading to the biomineralization of 61.7 g/l calcium carbonate in the presence of urea. TGA, XRD, and ESEM-EDX analyses proved calcite polymorph formation already within 16 h of incubation. Additionally, in presence of Pb²⁺, PG22 promoted the formation of cerussite (PbCO₃) and hydrocerussite [Pb₃(CO₃)₂(OH)₂], effectively removing 100 % of the Pb in solution, bioaccumulating 2 % and biomineralizing 98 %. The potential involvement of viable spores in the process could guarantee efficiency over time and in extreme conditions. These findings highlight L. sphaericus PG22's potential for MICP-based bioremediation strategies, offering a sustainable solution to restore marine and other polluted environments.