Shati, M.R., Weizmann Institute of Science, 76100 Rehovot, Israel
Rönen, D., Weizmann Institute of Science, 76100 Rehovot, Israel
Mandelbaum, R., Volcani Research Institute, 50250 Beit Dagan, Israel

A new method for the in situ study of bacterial activity in aquifers at microscale environments (scale order of centimeters) is presented. It is based on the use of a multilayer sampler (MLS) equipped with dialysis cells. Bacteria are confined inside the dialysis cells by membranes and are in continuous dynamic contact with groundwater. In the aquifer and within a vertical separation of only 7 cm between MLS cells, it was possible to detect atrazine reduction of 90% and concomitant dissolved oxygen reduction of ~45% in cells containing atrazine degrading bacteria, as compared to control cells not containing bacteria. This method enabled, for the first time, the demonstration of atrazine degradation by a pure bacterial culture of Pseudomonas sp. strain ADP in a contaminated aquifer (atrazine ≤ 450 μg/L). The bacteria introduced into the aquifer maintained their atrazine degradation ability even after being in contact with contaminated groundwater for 3 days. A major advantage of the MLS method is the combination of a sampling device and a minireactor (the dialysis cell) where the actual contact between bacteria and contaminants takes place. It allows for a simple mechanism of introduction and retrieval of bacteria and groundwater from predetermined sites in the aquifer. It is suggested that the present method may be used with other bacterial strains for evaluation of their activity in pristine or contaminated aquifers.A new method for the in situ study of bacterial activity in aquifers at microscale environments (scale order of centimeters) is presented. It is based on the use of a multilayer sampler (MLS) equipped with dialysis cells. Bacteria are confined inside the dialysis cells by membranes and are in continuous dynamic contact with groundwater. In the aquifer and within a vertical separation of only 7 cm between MLS cells, it was possible to detect atrazine reduction of 90% and concominant dissolved oxygen reduction of nearly 45% in cells containing atrazine degrading bacteria, as compared to control cells not containing bacteria. This method enabled, for the first time, the demonstration of atrazine degradation by a pure bacterial culture of Pseudomonas sp. strain ADP in a contaminated aquifer (atrazine ≤450 μg/L). The bacteria introduced into the aquifer maintained their atrazine degradation ability even after being in cantact with contaminated groundwater for 3 days. A major advantage of the MLS method is the combination of a sampling device and a minireactor (the dialysis cell) where the actual contact between bacteria and contaminants takes place. It allows for a simple mechanism of introduction and retrieval of bacteria and groundwater from predetermined sites in the aquifer. It is suggested that the present method may be used with other bacterial strains for evaluation of their activity in pristine or contaminated aquifers.