Reductive dechlorination of halogenated phenols by a sulfate-reducing consortium

A sulfidogenic consortium enriched from an estuarine sediment utilized 4-chlorophenol as a sole source of carbon and energy. Reductive dechlorination as the initial step in chlorophenol degradation by the sulfate-reducing consortium was confirmed with the use of chloro-fluorophenols. Both 4-chloro-2-fluorophenol and 4-chloro-3-fluorophenol were dechlorinated, resulting in stoichiometric accumulation of 2-fluorophenol and 3-fluorophenol, respectively. The fluorophenols were not degraded further. Furthermore, phenol was detected as a transient intermediate during degradation of 4-chlorophenol in the presence of 3-fluorophenol. Reductive dechlorination was inhibited by molybdate and did not occur in the absence of sulfate. These results indicate that 4-chlorophenol is reductively dechlorinated to phenol under sulfate-reducing conditions and mineralization of the phenol ring to CO₂ is coupled to sulfate reduction.