BACTERIAL-DEGRADATION OF POLYCYCLIC AROMATIC-HYDROCARBONS ON AGAR PLATES - THE ROLE OF BIOSURFACTANTS

Colonies of a polycyclic aromatic hydrocarbon (PAH) degrading and bios urfactant producing strain of Pseudomonas marginalis PD-14B, pre-incub ated on nutrient agar plates, formed zones of clearing when the agar s urface was coated with phenanthrene. Application of a drop of the cell -free biosurfactant solution to the agar surface, followed by coating with phenanthrene film also produced a clear zone against the opaque b ackground of the PAH coating. The results indicate that bacterial colo nies generate transparent haloes not only as a result of PAH degradati on, as is generally concluded from such tests, but also by solubilizat ion of these hydrophobic compounds, mediated by biosurfactants release d by the cells into the agar zone surrounding the colony.