Per- and polyﬂuoroalkyl substances (PFAS), called “forever chemicals”, have strong carbon−ﬂuorine bonds that under typical environmental conditions are not broken down. So, they accumulate. PFAS in contaminated water is typically removed by activated carbon filters that are then incinerated.
Biodegradation as a means to remediate PFAS is currently being explored. However, no organism capable of complete defluorination of PFAS has yet been found. Nonetheless, researchers hope the so-called infallibility principle — that microbes can evolve to degrade essentially any substance — will hold.
One example of the infallibility principle is the degradation of polychlorinated biphenyls (PCB). For years scientists assumed that biodegradation of these tough compounds was impossible until the late 80’s when PCB dechlorination was attributed to bacteria. Dehalococcoides is capable of transferring electrons to PCB, kicking out chloride ions in the process; however, it is much easier to break carbon–chlorine bonds than carbon–fluorine bonds. Also, Dehalococcoides have evolved in the presence of chlorinated compounds, but naturally occurring fluorinated compounds are rare. One naturally occurring fluorinated compound is fluoroacetate, a chemical that can be produced by certain plants. However, fluoroacetate contains only one fluorine atom while PFAS compounds are enveloped by carbon-fluorine bonds.