Jorge R. Osman

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.

Stromatolites are organo-sedimentary structures found principally in seas and saline lakes that contain sheets of sediments and minerals formed by layers of microbial communities, which trap sediments and induce the precipitation of minerals. A living stromatolite from the alkaline Laguna Interna in the Salar de Atacama was collected and one of the fragments was deposited in an experimental aquarium for 18 months. We used Illumina sequencing of PCR-amplified V4 regions of 16S rRNA genes from total extracted DNA to identify the microbial populations. The chemical structure was studied using X-Ray Diffraction (XRD) and bench chemical methods. We found that members belonging to the Proteobacteria, Planctomycetes, Chloroflexi and Bacteroidetes phyla dominated the bacterial communities of the living and aquarium cultured samples. The potential metabolic functionality of the prokaryotic community reveals that sulfur, nitrogen, methane and carbon fixation metabolism functions are present in the samples. This study is the first to provide new insights into the prokaryotic community composition from this unusual aquatic desert site. Further studies will be helpful to obtain a better understanding of the biotic and abiotic mechanisms residing in stromatolites from Laguna Interna, as well as to have better knowledge about the formation of these biosignatures.