Polyaromatic hydrocarbons (PAHs) are resistant to microbial
degradation because of their low water solubility and complex
structure with two or more fused benzene rings (Antizar-Ladislao
et al., 2004). Since many PAHs are toxic and carcinogenic, their
accumulation in the environment is of great concern. A typical
source of PAH contamination in soil is coal-tar creosote, which was
commonly used to preserve and waterproof crossties and power
line poles. Particularly in Finland, former sawmill sites constitute a
major problem. In addition to PAHs, such soils may contain
chlorophenols, polychlorinated dibenzo-p-dioxins and -furans
(PCDD/F), and heavy metals (Kitunen et al., 1987).
Bacteria degrade PAH compounds by an assimilative process
where they gain carbon and energy for the growth, which typically