Polycyclic aromatic hydrocarbon degrading microorganisms in Great Lakes sediments

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Biodegradation is a chemical transformation process that may result in the decontamination of sediments. A criterion for the potential success of biodegradation is the ability of indigenous microorganisms to catabolize contaminants, such as polycyclic aromatic hydrocarbons (PAHs). The number of microorganisms displaying this ability may be influenced by the extent of their exposure to PAHs. In this study, microorganisms from Keweenaw Bay (Lake Superior) and Trenton Channel (Detroit River) sediments were isolated and enumerated for their abilities to oxidize PAHs. The results revealed that total viable cell counts and PAH-degrading viable cell counts were similar in samples from both sites. The number of distinct biotypes differed, however. The total biotype count was higher for Keweenaw Bay than Trenton Channel; 68 versus 57, respectively. But, Trenton Channel sediment exhibited a greater diversity of PAH-degrading biotypes; 18 compared to only 3 for Keweenaw Bay sediment with the latter being confined to the upper 0 and 15 cm depths of the sediment core. Of the biotypes tested, 12 of 40 from Keweenaw Bay and 14 of 49 from Trenton Channel possessed the ability to denitrify. However, only 1 of 3 from Keweenaw Bay while 4 of 18 PAH-degrading biotypes from Trenton Channel could denitrify. Statistical analysis indicated that the number of PAH-degrading biotypes, the majority of which were identified as Gram negative rods, was site dependent. This suggested that contaminant exposure, an apparent major difference between the two sites, influences the relative percentage of PAH-degrading biotypes in sediments.

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Journal of Great Lakes Research