BIODEGRADATION OF AROMATIC-HYDROCARBONS IN AN EXTREMELY ACIDIC ENVIRONMENT

The potential for biodegradation of aromatic hydrocarbons was evaluate d in soil samples recovered slang gradients of both contaminant levels and pH values existing downstream of a long-term coal pile storage ba sin. pH values for areas greatly impacted by runoff from the storage b asin were 2.0. Even at such a reduced pH, the indigenous microbial com munity was metabolically active, showing the ability to oxidize more t han 40% of the parent hydrocarbons, naphthalene and toluene, to carbon dioxide and water. Treatment of the soil samples with cycloheximide i nhibited mineralization of the aromatic substrates, DNA hybridization analysis indicated that whole-community nucleic acids recovered from t hese samples did not hybridize with genes, such as nahA, nahG, nahH, t odC1C2, and tomA, that encode common enzymes from neutrophilic bacteri a. Since these data suggested that the degradation of aromatic compoun ds may involve a microbial consortium instead of individual acidophili c bacteria, experiments using microorganisms isolated from these sampl es were initiated, While no defined mixed cultures were able to evolve (CO2)-C-14 from labeled substrates in these mineralization experiment s, an undefined mixed culture including a fungus, a yeast, and several bacteria successfully metabolized approximately 27% of supplied napht halene after 1 week, This study shows that biodegradation of aromatic hydrocarbons can occur in environments with extremely low pf I values.