The effect of rhizosphere on growth of Sphingomonas chlorophenolica ATCC 39723 during pentachlorophenol (PCP) biodegradation in batch culture and soil

Abstract

Studies on the influence of the rhizosphere on the growth of Sphingomonas chlorophenolica during Pentacholophenol (PCP) degradation in batch culture and in soil were carried out. In batch culture, a basal minimal medium with or without rhizosphere exudates extracted from winter wheat was used. In soil systems, degradation experiments were performed in the presence and absence of plants. Measurements of PCP concentrations were made using high performance liquid chromatography analysis (HPLC). Bacterial analyses of S. chlorophenolica were carried out by plating on MSM medium. The results showed that the rhizosphere exudates stimulated the growth of the cells of S. chlorophenolica at concentrations of 50 and 80mg kg dry wt soil –1 as well as stimulating the ability of S. chlorophenolica to degrade PCP at a concentration of 80mg Kg dry wt soil -1. In addition, pentachlorophenol had an adverse effect on the growth of S. chlorophenolica. The introduction of S.chlorophenolica into the loamy soil with plants showed a faster degradation when compared to the inoculated soil without plants. There was a significant increase of S. chlorophenolica in the roots in comparison to those in the soil. This study showed that the presence of the inoculum S. chlorophenolica enhanced the PCP degradation in a loamy soil and it indicates the potential for a treatment process under a appropriate environmental conditions such as there present in soil systems