Detection and Quantification of Taste and Odor Producing Bacteria in Eagle Creek Reservoir

Abstract

The accelerated growth of algal blooms in water bodies has caused the increased occurrence of taste and odor (T&O) episodes worldwide. Even though T&O compounds have not been associated with adverse health effects, their presence can have extensive socio-economic impacts in contaminated waters. Eagle Creek Reservoir, a eutrophic water body, which supplies about 80% of Indianapolis drinking water, experiences frequent and sometimes severe odorous outbreaks. The terpenoid bacterial metabolites, 2-methylisoborneol (2-MIB) and geosmin, have been identified as the main compounds contributing to those T&O problems, which occur seasonally when the reservoir receives most of its water and nutrient loads from discharge events. In this study, ECR’s microbial community composition was assessed by a 16S next generation sequencing approach, confirming the presence of the major bacterial phyla of Cyanobacteria, Proteobacteria, Actinobacteria and Bacteroidetes, which are commonly found in freshwater environments. The relative abundance of Cyanobacteria, which are regarded as the main T&O producers in freshwater, followed the fluctuation of 2-MIB and geosmin concentrations closely. Mapping sequence analysis of a metagenomic dataset, successfully recovered the genes responsible for the synthesis of geosmin and 2-MIB, demonstrating the microbial ability for odorous compound production in ECR. Quantification of the geoA and MIBS genes in Cyanobacteria was achieved by the development and application of qPCR assays on water samples collected from the reservoir. A statistically significant positive correlation was found between MIBS gene quantity and MIB concentration for all sampling locations, implying that this assay could potentially be used as a tool for the early prediction of upcoming T&O episodes. The geoA gene detection assay, did not correlate well with geosmin concentrations, suggesting that even though the gene might be present, this does not necessarily mean that it is metabolically active.