Co-metabolic degradation of mono-fluorophenols by the ectomycorrhizal fungi Pisolithus tinctorius

The release of fluorinated organic compounds from fire retardants or agrochemical products may have a significant negative effect on soil ecosystems. In this study, the ability of Pisolithus tinctorius to tolerate and degrade mono-fluorophenols (FP) was assessed. In vitro studies showed fungal growth in the presence of 0.45 mM of 2-FP and 3-FP, but not in the presence of 4-FP. P. tinctorius was able to degrade up to 79% and 92% of 1 mM 2-FP and 3-FP, respectively, in glucose supplemented liquid medium, suggesting that 2- and 3-FP degradation occurred in co-metabolism with glucose consumption. 3-Fluorocatechol (FC) and 4-FC were identified as metabolic intermediates using HPLC and LC-MS. Liberation of fluoride was not detected suggesting that a fluorinated dead-end product was formed. In extracts of cells collected at the end of cultures supplemented with the mono-FPs, a metabolic intermediate compatible with a mass corresponding to a fluoromuconate compound, according to LC-MS data, was recovered. The results further suggest that ectomycorrhizal fungi may be able to degrade mono-FP in pure culture while using glucose as a carbon source, through a similar pathway as that found in bacteria. To our knowledge, this is the first time that degradation of mono-FPs by an ectomycorrhizal fungus is reported.