Polycyclic Aromatic Hydrocarbons (PAHs) form a group of toxic hydrophobic organic contaminants with low bioavailability for microbial attack in soil due to their low water solubility and sorption to organic matter. Some bacterial isolates are able to degrade AHs including 4-ring structures. These isolates are often Mycobacterium or Sphingomonas which seem to possess particular characteristics dealing with bioavailability issues, including direct contact of the PAH-degrading bact. with the pollutant source. However, the physiological mechanisms which play a role in adhesion and the ecological importance of adhesion in degrada- tion of PAHs in soil are not clear. This project aims at getting insight in the role of bact. adhesion to PAH-contaminated soil particles in PAH degradation in soil, in the mechanisms involved and in its ecological role in order to describe the micro-niche of PAH-degrading Mycobacterium and Sphingomonas.