Abstract:

Microbial communities play a significant role in the treatment of inorganic constituents at mine sites, often through direct metabolic reduction. Targeted quantitative polymerase chain reaction (qPCR) allows quantitative monitoring of specific genes involved in chemical reduction processes. Additionally, genetic colony identification and next generation sequencing (NGS) of 16S rRNA gene amplicons can be used to provide comprehensive microbial community profiles that are used to monitor important metabolic functions. In this study qPCR tests, NGS, and differential plating methods combined with genetic colony identification were used to detect and characterize microbial communities that reduced selenate (SeO₄^2-) to selenite (SeO₃^2-) or SeO₃^2- to elemental Selenium (Se).

Selenate metabolic pathways were used to develop specific qPCR tests which were used to quantify specialized SeO₄^2- reducing microbial communities. To monitor Se metabolism through NGS, a new functional category made from microbial taxa documented to be involved in Se reduction was added to a microbial functional database. The database was used to summarize the proportion of Se metabolizers in the context of other metabolic functions and indicated the presence of both specialized and non-specialized selenium reducers. Additionally, microbes from a known Se reducing site were plated and colonies of selenite reducing bacteria were grown and isolated. PCR amplification of the 16S rRNA gene combined with Sanger sequencing were used to identify the bacteria. This combination of novel and classic molecular biological tools provided multiple lenses to view selenium metabolizing communities and can increase our ability to understand how microbiology impacts treatment processes for selenium.

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Silvia Mancini