University of Utah Undergraduate Research Abstracts, Volume 3, Spring 2003

Monitoring the Effects of Bacteria Introduction on Native Bacterial Detachment in a Groundwater Aquifer

Suzanne Bethers Senior Biology [e-mail] Faculty Sponsor: William P. Johnson Dept. of Geology & Geophysics [e-mail] MONITORING THE EFFECTS OF BACTERIA INTRODUCTION ON NATIVE BACTERIAL DETACHMENT IN A GROUNDWATER AQUIFIER Using bacteria for subsurface remediation is an attractive option. In the past, aquifers were considered to be a relatively pure source of culinary water. Recently, subsurface contamination has been found to be considerably widespread. Bioremediation allows for inexpensive clean up of contamination without heavy equipment or introduction of additional toxins, but the details of bacteria remediation need to be explored further. This study focuses on the effect of introduced bacteria on the detachment behavior of bacteria already existing in the aquifer. Specifically, the bacteria were injected into the South Oyster aquifer in Virginia and samples were taken from wells throughout the aquifer. These samples were then taken to various research groups for analysis according to methods described in Johnson et al. (2001). This study focuses on tracking subsurface bacterial transport specifically at low concentrations. Using ferrographic capture, bacteria concentrations can be quantified at concentrations as low as 10 cells per milliliter (Zangetal. 1999). With this unique technique, the phenomenon of enhanced bacterial detachment was studied at the South Oyster aquifer in Virginia. The bacteria were tagged using an antibody specific to the strain. This antibody contains both a fluorescent tag, and an iron bead that allows the bacteria to be isolated on a small area of a slide. The bacteria then can be enumerated using an epifluores-cence microscope. The resulting data suggests that there was no increased detachment of existing bacteria by the introduction of a stained variant. The data also suggests that the introduced bacterial cells may have grown at the upper fringe of the plume-possibly due to greater availability of oxygen. This was concluded during enumeration by direct observation of cells showing a polar distribution of stain (Fig 1), indicating that stain was divided among the daughter cells during division. Fig1 Left: Bacteria showing polar distribution of stain under the epifluores-cence microscope. Right: Bacteria cells with even staining. 1 Johnson, W.P., Zhang, P., Gardner, P.M., Fuller, M.E., DeFlaun, M.F. (2001). Evidence for Detachment of Indiginous Bacteria from Aquifer Sediment in Response to Arrival of Injected Bacteria. Applied and Environmental Microbiology 67,4908-4913. 2.Zhang, P., Johnson, W.P.,Rowland, R. (1999). Bacterial Tracking Using Ferrographic Separation. Environ. Sci. 14 Technol. 33, 2456-2460.