Browsing by Subject "microbial source tracking"
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Item From Shipping to Swimming: Bacterial Monitoring and Diversity in Ballast Treatment Systems and Recreational Waters(2021-08) DeGuire, LisaThe use of indicator organisms as a proxy for pathogenic bacteria significantly reduces the cost and complexity of monitoring aquatic systems. Fecal indicator bacteria, such as Escherichia coli and Enterococcus spp., are commonly used by governmental agencies in recreational beach monitoring, wastewater treatment, and more recently as a tool in ballast water management. This research utilized culture-based and molecular techniques (qPCR and DNA sequencing) to explore two different applications of indicator bacteria: (1) a bench-scale experiment to explore the effectiveness of ballast water treatment techniques in freshwater and (2) an investigation of the sources of fecal contamination in a small Lake Superior tributary and surrounding recreational beaches. The ballast experiment addressed whether indicator bacteria are truly representative of other potentially harmful microbes after treatment (UV light and chlorination), as well as the scale of post-treatment bacterial regrowth. Both treatment techniques resulted in 99% reductions in culturable indicator and heterotrophic bacteria immediately following treatment (68-99% reductions when measured by qPCR). After 5 days, however, both lab and field incubations showed considerable regrowth of total bacteria (not reflected in indicators) and a distinct shift in bacterial community composition, including the regrowth of multiple pathogen containing genera (particularly Acinetobacter, Flavobacterium, Pseudomonas). The microbial source tracking project used library-independent and library-dependent methods to identify the sources of elevated E. coli in the recreational waters of Two Harbors, MN. Culturable E. coli abundance was correlated with turbidity and storm events, while human fecal sources appeared to be site-specific and independent from weather conditions. Both projects highlight the benefits and limitations of indicator bacteria in water quality monitoring and reinforce the importance of layering multiple analysis techniques to provide a more comprehensive understanding of microbial communities in ballast treatment systems and recreational waterways.Item A High-Throughput Microfluidic qPCR Platform for the Simultaneous Quantification of Fecal Indicator Bacteria, Microbial Source Tracking Markers, and Pathogens in Surface Waters and Municipal Wastewater(2022-07) Hill, ElizabethThe contamination of water with enteric pathogens is known to result in adverse human health outcomes. Untreated recreational waters may carry an increased risk of gastrointestinal illnesses for water recreators, especially if waters are contaminated with sewage. Current recreational water quality standards are based on outdated methods that cannot pinpoint fecal sources of pollution or accurately predict the risk of pathogen infection. There is a critical need to elucidate the correlations between fecal pollution sources and pathogens in recreational waters. This study expanded upon previous work to develop a novel Microfluidic qPCR (MFQPCR) platform for the simultaneous detection of microbial source tracking (MST) markers, fecal indicator bacteria (FIB), and pathogens in a single water sample. Eighty previously validated TaqMan probe-based assays were applied for use in 96.96 and 192.24 GE chips from Fluidigm. Results showed that 71 of these assays were capable of quantifying genes within acceptable qPCR quality criteria with uniform concentrations and cycling conditions. Multiple host-specific MST markers, FIB, and pathogens were quantified in wastewater influent and effluent, surface waters, and fecal samples. While virulence factor genes and pathogenic species were infrequently detected, a few significant relationships were observed between pathogens and human MST markers. By these associations, linear regression models were generated to estimate the occurrence of Mycobacteria spp. from MST marker quantities and additional physicochemical parameters. This MFQPCR technology is a promising tool for amassing comprehensive pathogen datasets. Downstream applications of these data, including Quantitative Microbial Risk Assessment, may be highly impactful in the development of strategies for more accurate and timely water quality monitoring.