Long-term and short-term inducible effects of trifluralin on Escherichia coli and Enterococcus faecalis

Abstract

In order to investigate the effects of the herbicide trifluralin on the indicator bacteria Escherichia coli and Enterococcus faecalis, these bacteria were inoculated into four different concentrations of trifluralin (0.1, 1, 10 and 100 μg/L). The bacterial growth was monitored turbidimetrically, followed by membrane filtration where membranes were placed on selective media agar. A non-typical morphology of colonies together with loss of culturability was recorded in all cases. Furthermore, differentiation in the strains' biochemical profiles was noted. E. coli was identified as Hafnia alvei and Ent. faecalis as Enterococcus faecium or Enterococcus avium. The current study suggests that the use of these two indicator bacteria in routine microbiological analysis of water might be questioned since trifluralin diluted to contaminated water has the potential to promote their growth and change their morphological and biochemical characteristics. © 2005 Taylor & Francis.