Microbiological analysis of cadmium-contaminated sediments during biostabilization with indigenous sulfate-reducing bacteria

Purpose: Sulfate-reducing bacteria (SRB) have received particular attention in the bioremediation of sediments contaminated with heavy metals. In this study, indigenous SRB were used to stabilize Cd in sediments spiked with different Cd concentrations (≤ 600 mg kg⁻¹). Materials and methods: The study investigated the Cd leaching efficiency from sediments after 166 days (d) of biotreatment and assessed the bacterial community and bacteria relationship in sediments during SRB biostabilization. Results and discussion: The study found that the Cd leaching efficiency of sediments was reduced by 18.1–40.3% (29.4 ± 8.7%) after 166 days of biotreatment. During the biostabilization, the bacterial community in sediments significantly changed, particularly after 61 days of biotreatment. At the family level, the identified dominant bacteria (mean abundance > 3%) included Bacillaceae, norank Nitrospira, Anaerolineaceae, Nitrospinaceae, Streptococcaceae, and Hydrogenophilaceae. The study also speculated the complex relationships between these bacteria. The relative abundance of Desulfobacteraceae and Desulfobulbaceae in sediments was enhanced after biotreatment. Bacillaceae and Streptococcaceae may play a negative role in Cd biostabilization and inhibited SRB biological activity. However, Anaerolineaceae and Hydrogenophilaceae may have commensalism and mutualism relationships, respectively, with typical SRB. The presence of Nitrospinacea and norank Nitrospira may reduce the inhibitive effect of denitrifying bacteria on SRB, thereby exhibiting a positive effect on biologic sulfate reduction and Cd biostabilization. Conclusions: Indigenous SRB treatment increased Cd stability in sediments and changed bacterial community. During SRB biostabilization, complex relationships between bacteria in sediments were speculated, including competition, syntrophism, and antagonism. These results provide insights for better regulating and controlling SRB biostabilization.