Formatted Title
Identification of Fluorotelomer Carboxylic Acid Degraders from Long-Term Enriched Sludge Consortia
Background/Objectives
Fluorotelomer-derived carboxylic acids (FTCAs) are industrial chemicals commonly detected in landfill leachates and environmental matrices. Unlike their perfluorinated analogues, FTCAs contain unfluorinated carbons which may facilitate microbial enzymatic activity. Wastewater sludges harbor diverse bacterial communities, many of which can transform a wide array of pollutants. To understand the biodegradability of FTCAs by mixed microbial consortia, we examined the potential of aerobic microbial communities from several wastewater treatment plants and soils to transform 5:3 and 6:2 FTCA. After multiple cycles of enrichments, we aimed to isolate and identify key players responsible for FTCA degradation and characterize genes/enzymes involved in biodefluorination.
Approach/Activities
First, biomass from six diverse sources was collected and exposed to high concentrations of 5:3 and 6:2 FTCAs (80 µM) as the sole carbon source and subjected to 1-year long domestication under aerobic conditions. Generation of free fluoride was monitored via ion selective electrode. FTCAs and their transformation products were analyzed by liquid chromatography tandem-mass spectrometry (LC-MS/MS). After evidence of FTCA transformation was demonstrated, consortia of interest were plated on a minimal media supplemented with FTCAs as the sole carbon and energy source to isolate potential degraders. The ability of FTCA by bacterial isolates was validated via resting cell assays. In parallel, 16 S rRNA amplicon-based sequencing was employed for microbial community analysis to reveal the dominant species in the consortia.
Results/Lessons Learned
Out of the six enrichments, two aerobic sludge consortia displayed constant fluoride release (0.582-5.579 µM) and decrease in FTCA concentrations (22-100%) with production of subsequent transformation products, such as unsaturated carboxylic acids (36-72 µg/L) and short-chain perfluorinated carboxylic acids (7-67 µg/L). From the enriched consortia derived from activated sludge, eight bacterial isolates were isolated based on their morphological characteristics and ability to subsist on minimal media supplemented with either 5:3 or 6:2 FTCA. Among these, two bacterial isolates were identified given their ability of defluorinating 6:2 FTCA over 48 hours (0.422-0.923 µM). These isolates were then identified as species belonging to the genera of Burkholderia and Achromobacter based on 16S rRNA gene sequencing. Whole genome sequencing of these isolates may decode the enzymes implicated in fluorotelomer transformation. Our results indicated FTCA aerobic degraders can be widely distributed. Discovery of new FTCA degrading isolates and associated molecular mechanisms enables the development of bioremediation strategies for the cleanup of FTCA-impacted environments.