| Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are fine-particle-associated atmospheric pollutants that present a threat to human health. Leaves of Tilia x euchlora (linden) infested by sooty mold fungi accumulate significantly higher amounts of these pollutants than leaves of Pyrus calleryana (pear) unaffected by molds. The difference in temperature dependence trends of buildup of PAHs on leaves of the two studied species of trees indicates that the presence of molds may alter the accumulation mode and/or degradation pathways of PAHs. Night-time degradation of particle-bound PAHs, physicochemical properties and composition of epicuticular waxes, and the possibility of enzymatic decomposition of PAHs while in close contact with fungi on leaves are the issues that need to be further studied.; Sooty mold fungi might play an important role, not only in accumulation of PAHs on leaves, but also in decomposition of PAHs in soil. Their role in degradation of PAHs in soil was investigated using four different sample types: Nonsterile Soil (NS) & Moldy Leaves (ML), Sterile Soil (SS) & ML, SS & ML & Bacteria (B), SS & Sterile Leaves (SL) & B.; The ATCC 13270 strain of the soil bacterium Stenotrophomonas maltophilia has not been previously studied for PAH-degrading capacity, but the genus was shown to degrade PAHs. The sooty mold fungi were composed of mitosporic ascomycetes and representatives of sexual Ascomycetes, Basidiomycetes, and Zygomycetes. The results showed that in the absence of natural soil microorganisms (SS+ML), sooty mold fungi significantly degraded anthracene, benz(a)anthracene, benzo(ghi)perylene, chrysene, fluoranthene, indeno(1,2,3-cd)pyrene, and phenanthrene. The tested soil bacterium was not able to degrade phenanthrene and fluorene, but it significantly degraded anthracene and benzo(b)fluoranthene, chrysene, dibenz(a,h)anthracene, indeno(1,2,3-cd)pyrene, benz(a)anthracene, and benzo(a)pyrene when inoculated in sterile soil and sterile leaves sample type as a pure culture (SS & SL & B). No synergism between the tested bacteria and sooty mold fungi in degradation of PAHs was observed. To the contrary, the microorganisms seemed to inhibit each other's activity. All tested PAHs but fluorene were degraded in NS & ML sample type. Hydrophobicity (Kow) was not a predictor of microbial degradation, but ionization potential seemed to have a threshold value beyond which bacterial degradation did not take place but fungal degradation did (i.e., Phe and Fla). However, Flu (which has the highest IP value) was not degraded by any of the studied sample sets. |
