BACTERIAL SURVIVAL AND THE FATE OF 15N IN ISOTOPE-ENRICHED ESCHERICHIA COLI IN PREPARATION FOR PATHOGEN TRACING

Karst aquifers are an important source of groundwater in Kentucky, supplying water in both rural and urban areas and supplementing the surface water of streams. The nature of karst aquifers and the ease with which unfiltered contaminants can enter make them particularly vulnerable to contamination. A novel tracer method using ¹⁵N as a bacterial label has been developed to track the transport of Escherichia coli, an indicator of contamination, through karst aquifers. Information on the fate of the ¹⁵N label, such as after the microorganism dies, can extend the applicability of the tracing method.

A wild strain of E. coli was isolated from the Cane Run groundwater basin in the Inner Bluegrass of Kentucky. Serotyping and virulence testing were performed to identify if the isolated strain had any of the characteristics of commonly pathogenic E. coli. Water samples were taken from Cane Run and used to set up microcosms, which were simultaneously sampled for the concentrations of the bacteria and the ¹⁵N label on six occasions over the course of 30 days.

The isolated E. coli did not have any common virulence factors, showing this strain’s potential for a viable trace in the groundwater basin. The data from the microcosms will be used to construct charts showing how the concentration of the ¹⁵N label changes as the bacteria survive and/or reproduce in the microcosms.