The biofilm environment offers a possible condition for inducing the competency of DNA recipient cells through nutritional starvation.

Transformation phenomena occurring under conditions mimicking the biofilm environment were investigated using Escherichia coli IM302 (as DNA recipient cells) and Providencia sp. WW2 (as surrounding cells in the biofilm model). In the case of planktonic IM302 cells kept at 25 degrees C, the transformation took place exclusively in the absence of organic nutrients (COD = 0), and was not substantially observed in the range of COD = 30-1500 mg O2/L. On the other hand, in the case of biofilm IM302 cells, the transformation occurred at relatively high levels under the examined conditions (temperature = 5 or 25 degrees C and COD = 0-1500 mg O2/L). These results indicated that the competency of biofilm IM302 cells was induced even in the presence of organic nutrients owing to nutritional starvation caused by WW2 cells.