Mineralization and transformation of monofluorophenols by Pseudonocardia benzenivorans

The aerobic metabolism of monofluorophenols (mono-FPs) by the actinomycete, Pseudonocardia benzenivorans, was studied. This strain was able to grow on 4-fluorophenol (4-FP) and readily transform 2- and 3-fluorophenol to the corresponding metabolites. The detailed mechanism of mono-FPs degradation by P. benzenivorans was elucidated from enzymatic assays and the identification of reaction intermediates by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry. Two types of fluorocatechols (i.e., 3- and 4-fluorocatechol) were identified as the key transformation products. During 4-FP degradation, only 4-fluorocatechol was detected, and a stoichiometric level of fluoride was released. Both fluorocatechols were observed together in cultures containing 3-fluorophenol (3-FP), while only 3-fluorocatechol was found to accumulate in 2-fluorophenol (2-FP)-containing cultures. Whole-cell extracts of P. benzenivorans expressed catechol 1,2-dioxygenase activity, indicating that the transformation of the three tested mono-FPs proceeded via ortho-cleavage pathway. The results presented in this paper provide comprehensive information regarding the metabolism of mono-FPs by a single bacterium.