Browsing by Author "Koltsidou, Ioanna"

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    Detection and Quantification of Taste and Odor Producing Bacteria in Eagle Creek Reservoir
    (2019-08) Koltsidou, Ioanna; Picard, Christine J.; Druschel, Gregory K.; Anderson, Gregory G.
    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.
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    Prevalence of Actinobacteria in the production of 2-methylisoborneol and geosmin, over Cyanobacteria in a temperate eutrophic reservoir
    (Elsevier, 2022-03) Clercin, Nicolas A.; Koltsidou, Ioanna; Picard, Christine J.; Druschel, Gregory K.; Earth Sciences, School of Science
    Commonly detected in surface waters worldwide, odorous compounds such as geosmin (GSM) and 2-methylisoborneol (MIB) pose important issues in drinking water and aquaculture industries. Impaired waters are frequently plagued by severe Cyanobacterial blooms and seasonal occurrences of Actinobacteria due to increased anthropogenic stressors as well as climate change that negatively impact the quality of water resources globally. Historically, studies have focused on the identification of key environmental factors and organisms involved in the production of GSM and MIB. This past decade, fast-evolving molecular techniques have greatly contributed to document the structure of bacterioplankton communities. Eagle Creek Reservoir, a eutrophic temperate reservoir, is frequently impacted by seasonal odorous episodes. During the spring 2013 outbreak of MIB and GSM (120.9 and 51.4 ng L−1, respectively), a shotgun metagenomics approach illustrated the dominance of Actinobacteria, Proteobacteria, Firmicutes, Bacteroidetes and Cyanobacteria in the reservoir waters. A network analysis highlighted interrelationships between bacterial taxa and environmental factors, and revealed two major clusters of bacteria: Cluster I driven by temperature and nitrate nitrogen and, Cluster II reflective of elevated concentrations of MIB and GSM. Analysis of 16S-based sequences recovered prevalently MIB- and GSM-encoding gene sequences belonging to several Actinobacteria (genus Streptomyces) rather than Cyanobacteria, formerly assumed to be the main producers. The use of genetics shifted our perception and stressed the role of Actinobacteria in the biosynthesis of odorous metabolites through the non-mevalonate pathway; as well as the detection of non-producing Arthrobacter potentially involved in the degradation of these compounds.