Field-scale evaluation of CFDA/SE staining coupled with multiple detectionmethods for assessing the transport of bacteria in situ

This research was undertaken to evaluate staining with the fluorescent comp ound CFDA/SE (5-(and-6-)-carboxyfluorescein diacetate, succinimidyl ester) coupled with multiple cell detection methodologies as a means to monitor ba cterial transport during field-scale experiments. Stained cells of Comamona s sp. strain DA001 were injected into a shallow, aerobic aquifer in Oyster, VA, USA. Groundwater samples analyzed in the laboratory using epifluoresce nce microscopy, flow cytometry, ferrographic separation, and microplate spe ctrofluorometry yielded comparable concentrations of CFDA/SE-stained DA001 cells, although each method had a different effective lower limit of detect ion. Determination of cell concentrations in the field using microplate spe ctrofluorometry allowed the track of the bacterial plume to be monitored in near-real time, but produced results that were not as accurate as laborato ry analyses. The CFDA/SE stain was well retained in the cells over a 5-mont h period. Normal handling of samples under fluorescent and incandescent lig hting did not significantly affect sample integrity, but exposure to sunlig ht resulted in rapid loss of total and per cell fluorescence. The combinati on of CFDA/SE staining and multiple detection methods was demonstrated as a n effective means to study bacterial transport in goundwater. (C) 2001 Fede ration of European Microbiological Societies. Published by Elsevier Science BN. All rights reserved.