Metagenomic insights into taxonomic diversity and metabolic potential of bacterial communities associated with tannery waste-contaminated soils

Abstract

Long-term exposure to anthropogenic stressors can lead to perturbations in microbiomes, either selecting for novel and biotechnologically important biotypes, or reductions in the microbial diversity and disequilibrium of ecosystem services. Consequently, analysis of variations in microbial structure and function in stressful environments remains a critical issue in microbial ecology. In this study, the taxonomic structure of bacterial communities inhabiting tannery waste dumpsite soils was evaluated comparatively with those from non-contaminated soils using 16S rRNA gene sequencing. Furthermore, the metabolic potential of these communities was inferred from community level physiological profiling fingerprints. The dumpsite has been receiving tannery waste since 1982; hence, the soils are laden with heavy metals including chromium, zinc, sodium, and potassium. Consequently, the following significant differences between bacterial communities from contaminated and non-contaminated soils were observed: (1) bacterial communities from the contaminated soils were characterized by lower species diversity, albeit at comparable species evenness (Simpson index); (2) long term contamination of soil shifted the bacterial community structure to a distinct core microbiome dominated by bacterial groups such as Halomonas, Balneolaceae, Aliifodinibius, Serinicoccus, Gracilimonas, Marinobater, Penticoccus, Fordinicurvata, Dietzia, and Norcadioides. These are characteristic of saline, metal-laden environments and have potentially high organo-pollutant degradative properties; and (3) bacterial communities from the contaminated soils exhibited a robust metabolic potential utilizing both natural and anthropogenically derived polymers at a higher rate. Overall, these results highlight tannery waste dumpsite soils as microbial diversity hotspots and potential reservoirs for exploration of novel biotechnological tools for bioremediation and industrial applications.