Acidimicrobium sp. Strain A6 (A6), which can use ammonium as electron donor and ferric iron as electron acceptor, via a process that has been coined Feammox, has also been shown to defluorinate PFAS, including perfluorinated compounds such as PFOA and PFOS, during the Feammox process. It has recently been shown that the genome of A6 contains the sequence for a reductive dehalogenase gene (rdhA), which is always expressed when PFAS are being defluorinated. Through batch incubations under a variety of conditions, it was observed that the defluorination rate of various PFAS correlates to the degree of expression of the rdhA gene. The rdhA sequence was then compared to sequences of other reductive dehalogenase genes, which revealed that several reductive dehalogenase genes with similarity to rdhA were present in other bacteria from the Acidimicrobiaceae family. A suite of PCR primers targeting these reductive dehalogenase genes was then designed and applied to 57 DNA samples extracted from sediments from various contaminated and pristine sites. Results revealed that the rdhA gene is involved in the defluorination of PFAS when their degradation by A6 was observed, and PFAW were not defluorinated when the rdhA gene was knocked out Work is ongoing to determine if the other genes for reductive dehalogenases with similarity to rdhA and identified in the Acidimicrobiaceae family can also independently be involved in the defluorination of PFAS.

Expression of reductive dehalogenase genes in Acidimicrobium sp. A6 during the defluorination of PFAS

ACS Spring 2022

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