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1. Escherichia coli efflux from rangeland ecosystems in the southcentral Great Plains of the United States

   https://doi.org/10.1002/jeq2.20527  

   Phillippe, Austin J. ; Wagner, Kevin L. ; Will, Rodney E. ; Zou, Chris B. ( January 2024 , Journal of Environmental Quality)

   Bacterial contamination of surface water is a public health concern. To quantify the efflux ofEscherichia coliinto ephemeral and intermittent streams and assess its numbers in relation to secondary body contact standards, we monitored runoff and measuredE. colinumbers from 10 experimental watersheds that differed in vegetation cover and cattle access in north‐central Oklahoma.Escherichia colinumbers were not significantly different among the watersheds, with one exception; the grazed prairie watershed (GP1) had greater numbers compared to one ungrazed prairie watershed (UP2). MedianE. colinumbers in runoff from ungrazed watersheds ranged from 260 to 1482 MPN/100 mL in comparison with grazed watersheds that ranged from 320 to 8878 MPN/100 mL. In the GP1 watershed, higher cattle stocking rates during pre‐ and post‐calving (February–May) resulted in significantly greater bacterial numbers and event loading compared to periods with lower stocking rates. The lack of significance among watersheds is likely due to the grazed sites being rotationally (and lightly) grazed, data variability, and wildlife contributions. To address wildlife sources, we used camera trap data to assess the usage in the watersheds; however, the average number of animals in a 24‐h period did not correlate with observed medianE. colinumbers. Because of its impacts onE. colinumbers in water, grazing management (stocking rate, rotation, and timing) should be considered for improving water quality in streams and reservoirs.

    

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2. Metagenomic Sequencing and Quantitative Real-Time PCR for Fecal Pollution Assessment in an Urban Watershed

   https://doi.org/10.3389/frwa.2021.626849  

   Brumfield, Kyle D. ; Cotruvo, Joseph A. ; Shanks, Orin C. ; Sivaganesan, Mano ; Hey, Jessica ; Hasan, Nur A. ; Huq, Anwar ; Colwell, Rita R. ; Leddy, Menu B. ( February 2021 , Frontiers in Water)

   null (Ed.)

   Microbial contamination of recreation waters is a major concern globally, with pollutants originating from many sources, including human and other animal wastes often introduced during storm events. Fecal contamination is traditionally monitored by employing culture methods targeting fecal indicator bacteria (FIB), namely E . coli and enterococci, which provides only limited information of a few microbial taxa and no information on their sources. Host-associated qPCR and metagenomic DNA sequencing are complementary methods for FIB monitoring that can provide enhanced understanding of microbial communities and sources of fecal pollution. Whole metagenome sequencing (WMS), quantitative real-time PCR (qPCR), and culture-based FIB tests were performed in an urban watershed before and after a rainfall event to determine the feasibility and application of employing a multi-assay approach for examining microbial content of ambient source waters. Cultivated E . coli and enterococci enumeration confirmed presence of fecal contamination in all samples exceeding local single sample recreational water quality thresholds ( E . coli , 410 MPN/100 mL; enterococci, 107 MPN/100 mL) following a rainfall. Test results obtained with qPCR showed concentrations of E . coli , enterococci, and human-associated genetic markers increased after rainfall by 1.52-, 1.26-, and 1.11-fold log 10 copies per 100 mL, respectively. Taxonomic analysis of the surface water microbiome and detection of antibiotic resistance genes, general FIB, and human-associated microorganisms were also employed. Results showed that fecal contamination from multiple sources (human, avian, dog, and ruminant), as well as FIB, enteric microorganisms, and antibiotic resistance genes increased demonstrably after a storm event. In summary, the addition of qPCR and WMS to traditional surrogate techniques may provide enhanced characterization and improved understanding of microbial pollution sources in ambient waters. 

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3. Impact of Metazooplankton Filter Feeding on Escherichia coli under Variable Environmental Conditions

   https://doi.org/10.1128/AEM.02006-19  

   Ismail, Niveen S. ; Blokker, Brittney M. ; Feeney, Tyler R. ; Kohn, Ruby H. ; Liu, Jingyi ; Nelson, Vivian E. ; Ollive, Mariah C. ; Price, Sarah B. ; Underdah, Emma J. ; Stams, Alfons J. ( December 2019 , Applied and Environmental Microbiology)

   ABSTRACT The fecal indicator bacterial species Escherichia coli is an important measure of water quality and a leading cause of impaired surface waters. We investigated the impact of the filter-feeding metazooplankton Daphnia magna on the inactivation of E. coli . The E. coli clearance rates of these daphnids were calculated from a series of batch experiments conducted under variable environmental conditions. Batch system experiments of 24 to 48 h in duration were completed to test the impacts of bacterial concentration, organism density, temperature, and water type. The maximum clearance rate for adult D. magna organisms was 2 ml h −1 organism −1 . Less than 5% of E. coli removed from water by daphnids was recoverable from excretions. Sorption of E. coli on daphnid carapaces was not observed. As a comparison, the clearance rates of the freshwater rotifer Branchionus calyciflorus were also calculated for select conditions. The maximum clearance rate for B. calyciflorus was 6 × 10 −4  ml h −1 organism −1 . This research furthers our understanding of the impacts of metazooplankton predation on E. coli inactivation and the effects of environmental variables on filter feeding. Based on our results, metazooplankton can play an important role in the reduction of E. coli in natural treatment systems under environmentally relevant conditions. IMPORTANCE Escherichia coli is a fecal indicator bacterial species monitored by the U.S. Environmental Protection Agency to assess microbial water quality. Due to the potential human health implications linked to high levels of E. coli , it is important to understand the inactivation or reduction mechanisms in surface waters. Our research examines the capacities of two types of widespread filter-feeding freshwater metazooplankton, Daphnia magna and Brachionus calyciflorus , to reduce E. coli concentrations. We examine the impacts of different environmentally relevant conditions on the clearance rates. Our results contribute to a better understanding of the importance of metazooplankton in controlling E. coli concentrations and what conditions will reduce or increase grazing. These results provide baseline data to support future efforts to develop a quantitative model relating zooplankton uptake rates to relevant environmental variables. 

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4. Host and Water Microbiota Are Differentially Linked to Potential Human Pathogen Accumulation in Oysters

   https://doi.org/10.1128/aem.00318-23  

   Diner, Rachel E. ; Zimmer-Faust, Amy ; Cooksey, Emily ; Allard, Sarah ; Kodera, Sho M. ; Kunselman, Emily ; Garodia, Yash ; Verhougstraete, Marc P. ; Allen, Andrew E. ; Griffith, John ; et al ( July 2023 , Applied and Environmental Microbiology)

   Dudley, Edward G. (Ed.)

   Oysters play an important role in coastal ecology and are a globally popular seafood source. However, their filter-feeding lifestyle enables coastal pathogens, toxins, and pollutants to accumulate in their tissues, potentially endangering human health. While pathogen concentrations in coastal waters are often linked to environmental conditions and runoff events, these do not always correlate with pathogen concentrations in oysters. Additional factors related to the microbial ecology of pathogenic bacteria and their relationship with oyster hosts likely play a role in accumulation but are poorly understood. In this study, we investigated whether microbial communities in water and oysters were linked to accumulation of Vibrio parahaemolyticus, Vibrio vulnificus, or fecal indicator bacteria. Site-specific environmental conditions significantly influenced microbial communities and potential pathogen concentrations in water. Oyster microbial communities, however, exhibited less variability in microbial community diversity and accumulation of target bacteria overall and were less impacted by environmental differences between sites. Instead, changes in specific microbial taxa in oyster and water samples, particularly in oyster digestive glands, were linked to elevated levels of potential pathogens. For example, increased levels of V. parahaemolyticus were associated with higher relative abundances of cyanobacteria, which could represent an environmental vector for Vibrio spp. transport, and with decreased relative abundance of Mycoplasma and other key members of the oyster digestive gland microbiota. These findings suggest that host and microbial factors, in addition to environmental variables, may influence pathogen accumulation in oysters. 

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5. Removal of Fecal Indicator Bacteria by River Networks

   https://doi.org/10.3390/w14040617  

   Huang, Tao ; Wollheim, Wilfred M. ; Jones, Stephen H. ( February 2022 , Water)

   Fecal contamination is a significant source of water quality impairment globally. Aquatic ecosystems can provide an important ecosystem service of fecal contamination removal. Understanding the processes that regulate the removal of fecal contamination among river networks across flow conditions is critical. We applied a river network model, the Framework for Aquatic Modeling in the Earth System (FrAMES-Ecoli), to quantify removal of fecal indicator bacteria by river networks across flow conditions during summers in a series of New England watersheds of different characteristics. FrAMES-Ecoli simulates sources, transport, and riverine removal of Escherichia coli (E. coli). Aquatic E. coli removal was simulated in both the water column and the hyporheic zone, and is a function of hydraulic conditions, flow exchange rates with the hyporheic zone, and die-off in each compartment. We found that, at the river network scale during summers, removal by river networks can be high (19–99%) with variability controlled by hydrologic conditions, watershed size, and distribution of sources in the watershed. Hydrology controls much of the variability, with 68–99% of network scale inputs removed under base flow conditions and 19–85% removed during storm events. Removal by the water column alone could not explain the observed pattern in E. coli, suggesting that processes such as hyporheic removal must be considered. These results suggest that river network removal of fecal indicator bacteria should be taken into consideration in managing fecal contamination at critical downstream receiving waters. 

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