Development of eukaryotic zoospores within polycyclic aromatic hydrocarbon (PAH)-polluted environments: a set of behaviors that are relevant for bioremediation.

In this study, we assessed the development (formation, taxis and settlement) of eukaryotic zoospores under different regimes of exposure to polycyclic aromatic hydrocarbons (PAHs), which imitated environmental scenarios of pollution and bioremediation. With this aim, we used an oomycete, Pythium aphanidermatum, as a source of zoospores and two PAH-degrading bacteria (Mycobacterium gilvum VM552 and Pseudomonas putida G7). The oomycete and both bacteria were not antagonistic, and zoospore formation was diminished only in the presence of the highest bacterial cell density (10(8)-10(10) colony-forming units mL(-1)). A negative influence of PAHs on zoospore formation and taxis was observed when PAHs were exposed in combination with organic solutions and polar solvents. Co-exposure of PAHs with non-polar solvents [hexadecane (HD) and 2,2,4,4,6,8,8-heptamethylnonane (HMN)] did not affect zoospore settlement at the interfaces of the organic solvents and water. However, zoospores settled and created mycelial networks only at HD-water interfaces. Both bacteria diminished the toxic influence of PAHs on zoospore formation and taxis, and they did not interrupt zoospore settlement. The results suggest that zoospore development could be applicable for toxicity assessment of PAHs and enhancement of their bioavailability. Microbial interactions during both swimming modes and community formation at pollutant interfaces were revealed as major factors that have potential relevance to bioremediation.