The biorecovery of europium (Eu) from primary (mineral deposits) and secondary (mining wastes) resources is of interest due to its remarkable luminescence properties, important for modern technological applications. In this study, we explored the tolerance levels, reduction and intracellular bioaccumulation of Eu by a site-specific bacterium,Clostridiumsp. 2611 isolated from Phalaborwa carbonatite complex.Clostridiumsp. 2611 was able to grow in minimal medium containing 0.5 mM Eu³⁺. SEM-EDX analysis confirmed an association between Eu precipitates and the bacterium, while TEM-EDX analysis indicated intracellular accumulation of Eu. According to the HR-XPS analysis, the bacterium was able to reduce Eu³⁺to Eu²⁺under growth and non-growth conditions. Preliminary protein characterization seems to indicate that a cytoplasmic pyruvate oxidoreductase is responsible for Eu bioreduction. These findings suggest the bioreduction of Eu³⁺byClostridiumsp. as a resistance mechanism, can be exploited for the biorecovery of this metal.

Emerging contaminants (ECs) are organic compounds, including pharmaceuticals, personal care products, pesticides, and other chemicals, that are linked to harmful effects on aquatic environments. Indigenous microorganisms often act as natural barriers by breaking down these contaminants into less harmful substances. However, not all biological processes result in the complete biodegradation of ECs, and specific conditions must be met for this to occur. These conditions are influenced by chemical and biological factors such as seasonal variations, oxygen availability, nutrient levels, ECs concentrations, and the types of microorganisms present in the aquatic environment, all of which can either enhance or inhibit ECs biodegradation. This review provides a thorough examination of the chemical properties and factors that influence the fate of ECs in aquatic environments, discussing the impact of these factors on microbial degradation of ECs through metabolic and co-metabolic processes. Finally, this review emphasizes the importance of integrating interdisciplinary studies that consider diverse key factors to offer a more holistic and accurate understanding of ECs’ biodegradation in aquatic systems.

Emerging contaminants have gained interest over the years due to their adverse effects on the aquatic environment. Therefore, it is essential to improve the current strategies for their removal. Biodegradation has emerged as an efficient strategy driven by microorganisms through metabolism and co-metabolism pathways. Enzymes encoded by specific genes facilitate these processes. This study aimed to identify and quantify the genes involved in these pathways. The research identified bacterial species belonging to the genera Pseudomonas, Nitrosomonas, Nitrosospira, and Methylotenera, which are associated with the degradation of emerging contaminants. Additionally, it successfully identified genes linked to metabolism and co-metabolism processes within the indigenous bacteria (MAGs). The findings suggest that the native bacteria in the samples may have the natural potential to mitigate emerging contaminants in aquatic environments through the combined actions of metabolism and co-metabolism.