Differential Transport of Escherichia coli Isolates Compared to Abiotic Tracers in a Karst Aquifer

Ashley M. Bandy, Kimberly Cook, Alan E. Fryar, Junfeng Zhu

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Lack of filtration and rapid transport of groundwater and particulate matter make karst aquifers susceptible to bacterial contamination. This study utilized quantitative polymerase chain reaction (qPCR) to examine the transport and attenuation of two nonvirulent isolates of Escherichia coli (E. coli) in relation to traditional groundwater tracers (rhodamine WT dye and 1-µm diameter latex microspheres) in a karst-conduit aquifer in central Kentucky. Bacterial isolates were labeled with stable isotopes (15N and 13C). All tracers were detected more than 6 km downstream from the injection site and demonstrated overlapping breakthrough curves, with differential transport observed between the two bacterial strains. The E. coli isolate containing the kps gene (low attachment) arrived at sampling sites 1.25 to 36 h prior to the bacterial isolate containing the iha gene (high attachment) and was detected in samples collected following storm events in which the iha isolate was not detected. The storage potential of contaminants within karst systems was demonstrated by the remobilization of all tracers during storm events more than 1 month after injection. Bacteria-sized microspheres were more easily remobilized during periods of increased discharge compared to other tracers. The study demonstrated that molecular biology techniques such as qPCR can be utilized as a sensitive analysis of bacterial tracers in karst aquifers and may prove to be a more sensitive analytical technique than stable isotope analysis for field-scale traces.

Original languageEnglish
Pages (from-to)70-78
Number of pages9
Issue number1
StatePublished - Jan 1 2020

Bibliographical note

Funding Information:
This work was supported by Agriculture and Food Research Initiative Competitive Grant No. 2013-67011-21278 from the USDA National Institute of Food and Agriculture, a Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) Pathfinder Fellowship, the Cave Research Foundation, the Geological Society of America, and the University of Kentucky. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture or other funding agencies. The authors are grateful to people who helped made this project possible: Rohan Parekh at the USDA-AWMRU, Tricia Coakley and John May at the University of Kentucky (UK) Environmental Research Training Laboratories, staff at the Georgetown Municipal Water and Sewer Service and the Kentucky Geological Survey, and students in the UK Department of Earth and Environmental Science. The authors would also like to thank Melissa Lenczewski, Anita Anderson, and an anonymous reviewer for insightful comments that improved the manuscript.

Publisher Copyright:
© 2019, National Ground Water Association.

ASJC Scopus subject areas

  • Water Science and Technology
  • Computers in Earth Sciences


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