THE USE OF FLUORESCENCE IN SITU HYBRIDIZATION METHOD ON SOIL AND WATER ECOSYSTEMS: A NEW APPROACH TO STUDY THE EFFECT OF PESTICIDES ON BACTERIAL COMMUNITY

Groundwater quality and pesticide contamination of aquifers have become of great concern in all countries in which populations rely on this resource for drinking water. The transport of pesticides from agricultural fields to groundwater bodies is mainly due to water infiltration through soil. The ability of soil and groundwater to recover from pesticide contamination depends primarily on the presence of a microbial community able to degrade them. Nevertheless, there has been little research on these microrganisms because it relies on methods able to identify and characterize their community structure and functioning. For example, most bacteria living in oligotrophic conditions are unable to grow on classic culture media. The use of molecular methods makes it possible to overcome this kind of identification limitation. In the present work the Fluorescence In Situ Hybridization (FISH) method has been applied to both soil and groundwater samples treated with s-triazines (simazine and terbuthylazine). The bacterial community structure in the presence and in the absence of the herbicides have been compared. The use of 16S rRNA-targeted oligonucleotide probes, designed specifically for the main phylogenetic levels (Archaea, Eubacteria, Alpha- Beta- Gamma-subdivision of Proteobacteria, Plantomycetes and Gram-positive bacteria with a high DNA G+C content), and a DAPI stain made it possible to assess the structure of the bacterial community and its changing in the presence of the herbicides.