Mineralization mechanism and pollutant immobilization characteristics of vaterite induced by Bacillus velezensis and Pseudomonas putida

Exploring strain-specific differences in bacterial vaterite biomineralization can supplement the basic theoretical research of biomineralization and reveal the biogeochemical linkages between microbially induced carbonate formation and in-situ pollutant sequestration in soil environments. In this study, Bacillus velezensis LB002 and Pseudomonas putida KT2440 were used as representative bacterial strains to compare strain-dependent vaterite formation and pollutant sequestration behavior. The biomineralization processes in the liquid medium were dynamically monitored, and the induced biominerals were characterized, with particular attention to their organic components. The differences in vaterite characteristics between both bacterial systems were evaluated, and their sequestration performance was assessed taking Cu 2+ and tetracycline as target pollutants. Both strains induced vaterite formation under identical culture conditions, while B. velezensis exhibited a stronger biomineralization capacity than P. putida . In a 100 mL culture system, the Ca 2+ mineralization percentage of B. velezensis reached 35.06%, and the dry weights of biomineral aggregates produced by B. velezensis and P. putida were 0.36 and 0.31 g, respectively. SEM observations revealed that the vaterite induced by B. velezensis had a loose and porous surface, whereas that induced by P. putida had a relatively smooth surface. For the high concentration of Cu 2+ at 50 mg/L, the sequestration rate reached 84.93% for B. velezensis -induced vaterite, compared with 71.86% for P. putida -induced vaterite under the same conditions. Both biominerals demonstrated similar tetracycline sequestration efficiency, with values of approximately 60%. This study verifies that these two representative bacterial strains differ markedly in biogenic vaterite formation and mineral-mediated pollutant sequestration capacity, with interspecific variations in cell wall, EPS and CA activity accounting for these strain-dependent disparities. These findings help interpret why soil carbonate minerals show heterogeneous pollutant immobilization effects in natural edaphic environments, and offer experimental evidence for understanding microbe–carbonate–contaminant coupled biogeochemical cycling within soils and sediments.