The subsurface recalcitrance of perfluoroalkyl
acids (PFAAs) derived
from aqueous film-forming foams could have adverse impacts on the
microbiological processes used for the bioremediation of co-mingled
chlorinated solvents such as trichloroethene (TCE). Here, we show
that reductive dechlorination by a methanogenic, mixed culture was
significantly inhibited when exposed to concentrations representative
of PFAA source zones (>66 mg/L total of 11 PFAA analytes, 6 mg/L
each).
TCE dechlorination, cis-dichloroethene and vinyl chloride production
and dechlorination, and ethene generation were all inhibited at these
PFAA concentrations. Phylogenetic analysis revealed that the abundances
of 65% of the operational taxonomic units (OTUs) changed significantly
when grown in the presence of PFAAs, although repression or enhancement
resulting from PFAA exposure did not correlate with putative function
or phylogeny. Notably, there was significant repression of Dehalococcoides (8-fold decrease in abundance) coupled
with a corresponding enhancement of methane-generating Archaea (a
9-fold increase). Growth and dechlorination by axenic cultures of Dehalococcoides mccartyi strain 195 were similarly
repressed under these conditions, confirming an inhibitory response
of this pivotal genus to PFAA presence. These results suggest that
chlorinated solvent bioattenuation rates could be impeded in subsurface
environments near PFAA source zones
