Molecular Characterization of Potential Geosmin-producing Cyanobacteria from Lake Ontario

Geosmin is an odorous secondary metabolite produced by some cyanobacteria during growth and released from the cells. Little is known about the biosynthesis of geosmin and the gene(s) required for its production have not been characterized. During late August and early September geosmin episodes due to planktonic cyanobacteria frequently occur in the northwest basin of Lake Ontario waters resulting in taste and odour episodes in drinking water that serves more than 5 million people. At high concentrations geosmin evades traditional drinking water treatment and reaches the tap. These episodes often elicit consumer concern and are wrongly construed to reflect impaired drinking water safety. Water quality managers in the region have generally been unable to prevent or control taste and odour episodes via a proactive approach due to the lack of knowledge of cyanobacterial communities in offshore waters as well as the inability to predict when geosmin will reach intake pipes due to downwelling, the process by which the surface waters mix with the hypolimnion. This study evaluated denaturing gradient gel electrophoresis (DGGE) as a molecular tool for proactive monitoring of potential taste and odour-causing cyanobacteria in environmental samples. The 16S rRNA gene was assessed for its ability to distinguish among geosmin-producing and non-producing strains. This study also examined the evolutionary relationships among geosmin-producing cyanobacteria using the full-length 16S rRNA gene and compared phylogenies with current taxonomy. A DGGE standard using the V3 hypervariable region of the 16S rRNA gene was developed using geosmin-producing and non-producing isolates of cyanobacteria. Included