We investigated the abundance of Pseudanabaena species and the concentration of the monoterpene 2-methylisoborneol (2-MIB) from July to October at three sampling sites in South Korea. To identify the main cause of 2-MIB occurrence in drinking water source, we characterized and performed a phylogenetic analysis of the 2-MIB synthase gene. Pseudanabaena was the dominant cyanobacterium (68%-100%) among the samples. At all three sampling sites, a strong positive correlation was detected between 2-MIB concentrations and Pseudanabaena cell numbers. A phylogenetic analysis of 222 MIB sequences isolated from the water samples showed that all of the clones were affiliated with the Pseudanabaena MIB synthase gene, demonstrating that the 2-MIB in the Han River drinking water source was produced by Pseudanabaena sp. Using a clone of the 2-MIB gene, network-based analysis and unweighted pair group method with arithmetic mean analysis were used to examine temporal and spatial variation in the 2-MIB concentration and Pseudanabaena abundance. The network analysis showed greater temporal than spatial similarity among the 2-MIB gene clones. Together, our results demonstrate that Pseudanabaena was the main producer of 2-MIB. These findings provide important information for odour management in drinking water source.
