Soil extracts and co-culture assist biodegradation of 2,4,6-tribromophenol in culture and soil by an auxotrophic Achromobacter piechaudii strain TBPZ

Achromobacter piechaudii strain TBPZ is a 2,4,6-tribromophenol (TBP) degrader that was isolated from contaminated desert soil. In the current study we have found that yeast extract has a substantial impact on the debromination activity of non-dividing cells of TBPZ harvested during the stationary phase. The results suggest that yeast extract provides a factor that is necessary for activity and that is missing in stationary cells. Nevertheless, strain TBPZ from the stationary phase did survive and degrade TBP in soils with different degrees of contamination without yeast extract supplements. Experiments with soil extracts showed that a soluble factors is responsible for this phenomenon in a similar way to yeast extract. To test whether other soil bacteria provide these factors, co-culture experiments with strain TBPZ and a bisphenol A (BPA) degrader, Sphingomonas strain WH1, that was isolated from the same contaminated desert soil, were carried out. These experiments clearly demonstrated that growth of strain WH1 on BPA enables strain TBPZ to degrade TBP rapidly, suggesting that a metabolic product from WH1 is involved. In experiments with mixed amino acid blend (casamino acid), slower growth was observed when compared to growth with yeast extract. Providing vitamins and a defined mixture of two amino acids, tryptophan and phenylalanie, caused rapid degradation of TBP without the rapid growth seen in yeast extract treatment, indicating that the amino acids are needed to sustain biodegradation activity. The results of this study highlight that degradation of TBP by strain TBPZ is possibly controlled by micronutrients. In addition, the results suggest that an auxotrophic bacterium able to degrade halo-organic pollutants can survive in a natural environment due to its interaction with natural organic matter or other microorganisms.