Abundance of nagAc naphthalene dioxygenase gene measured using real-time pcr is correlated with naphthalene concentrations in freshwater sediments

HEBE DIONISI; CHRISTOPHER CHEWNING; KATHERINE MORGAN; FU MIN MENN; JAMES EASTER; VIJAY VULAVA; GARY SAYLER

San Carlos de Bariloche

Congreso; XXXIX Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2003

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Chattanooga Creek is one of the most polluted waterways in the southeastern United States. Chemical analysis of creek sediments indicated moderate to high levels of polycyclic aromatic hydrocarbons, with naphthalene concentrations between 0.1 and 105.64 mg/kg of dry sediment. The objective of this study was to quantify genes encoding for the naphthalene dioxygenase enzyme using TaqMan real-time PCR. An assay was designed and optimized for the quantification of nagAc-like genes using conserved regions in this gene cloned from Ralstonia sp. U2 and 41 related sequences from pure cultures and uncultured bacteria. The assay indicated the presence of 4.10 ± 0.66 x 103 to 2.87 ± 0.34 x 105 copies of nagAc-like gene per mg of DNA extracted from sediments of Chattanooga Creek. These values corresponded to 1.15 ± 0.56 x 105 to 5.35 ± 0.41 x 107 copies of this target per g of dry sediment. A positive correlation was found between naphthalene concentrations and copies of nagAc target per mg of DNA (r2 = 0.747) and per g of dry sediment (r2 = 0.586). A real-time PCR system targeting the 16S rRNA gene of most bacteria indicated the presence of approximately equal concentrations of this target (1.31 ± 0.42 x 109) per mg of DNA in all analyzed samples. These results indicate significant differences in the population of Bacteria carrying nagAc-like genes in sediments of Chattanooga Creek with different naphthalene concentrations.