Bioaccumulation and enhanced persistence of the acaricide Dicofol by Azospirillum lipoferum

The purpose of this paper is to study the influence of the Gram-negative nitrogen-fixing bacterium Azospirillum lipoferum in the persistence of the organochlorine acaricide Dicofol [1,1-bis(4′-chlorophenyl)2,2,2-tricholoro-ethanol]. This microorganism bioaccumulates dicofol and the bioconcentration factor reaches 577 at the maximum after 3 days of incubation as measured by GC-MS. Cell uptake of (U-14C) Dicofol measured by photo-induced binding technique shows similar results. Incorporation of (U-14C)Dicofol in A. lipoferum reaches equilibrium in 20 minutes, it is not temperature dependent, and acaricide-cell interactions occur preferentially to cell envelope. Dicofol is easily hydrolised in aqueous cell-free medium (67%) and was less degraded in the presence of A. lipoferum cells (31%). This means that Dicofol bioaccumulation in A. lipoferum protected this acaricide against hydrolysis. As a consequence Dicofol-cell interactions can enhance the persistence of this chemical in the soil.