## 3 Results
### Atrazine Degrading Genetic Potential of Groundwater Bacterial Isolates  
Atrazine-degrading genetic potential of each isolated bacteria was determined by PCR screening for the specific genes _atzA,B,C,D,E,F_ and _trzN,D_ coding for enzymes responsible for atrazine transformation (Figure 2). Amplification by PCR allows for the estimation of the presence/absence of the genes involved in the atrazine degradation metabolic pathway, which gives an idea of the genetic potential of groundwater or isolated bacteria to carry out this pathway. The results of the PCR amplification assays using groundwater community DNA as a template revealed the presence of _atzA_, _atzB_, _atzC_, _atzE_, _atzF_, _trzN_, and _trzD_ sequences (see Table 4). No PCR products were obtained for the _atzD_ gene \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Family** & **Closest Type Strain Associated** & **No. of Clones** & **RA 1 (\%)** \\ \hline Pseudomonas alcaligenes NEB 585 & 1 & \\ Pseudomonas alcaligenes ALI5-21 & 1 & \\ Pseudomonas azodorurans NBRC 12693 & 2 & \\ Pseudomonas cedrina CFML 96-198 & 1 & \\ Pseudomonas chengduensis MBR & 1 & \\ Pseudomonas gessardii CIP 105469 & 5 & 29.2 \\ Pseudomonas libanensis CIP 105460 & 1 & \\ Pseudomonas paralactis DSM 29164 & 10 & \\ Pseudomonas pseudolcaligenes [PERSON] 63 & 2 & \\ Pseudomonas resirovomas ATCC 14235 & 1 & \\ Pseudomonas silesiensis A3 & 1 & \\ Acidorox facillus LMG 2193 & 1 & \\ Comamonas phosphate WYH 22-41 & 1 & \\ Commonadaceae & Hydrogenophag atypica BS 41.8 & 1 & 29.2 \\ Hydrogenophaga taeinespiralis 2K1 & 21 & \\ Ramlibacher ginsengidiumtutans BXN5-27 & 2 & \\ Sphingomonad alcet K-1-16 & 1 & \\ Sphingomygia biauzamenis B230 & 7 & 10.1 \\ Sphingomygia fribereopsis Kp5.2 & 1 & \\ Moraxellaceae & Acinetobacter johnsoni ATCC 17909 & 5 & 9.0 \\ Acinetobacter sebahenesis SW-100 & 3 & \\ Pararheinheimera aquatica GR5 & 1 & \\ Chromatiaceae & Pararheinheimera chironomi K19414 & 4 & \\ Pararheinheimera mesophila IITR-13 & 1 & 9.0 \\ Pararheinheimera texasensis A62-14B & 2 & \\ Brevenundinomas vesicularus Busing & 1 & \\ Cheptbolacteraceae & Phenylobacterium immobile E & 1 & \\ Cheptbolacterium mobile GA26 & 1 & \\ Phenylobacterium muchangponense A8 & 1 & \\ Xanthomonadaceae & Arentomonas mataiensis YT8 & 1 & \\ Stenotrophomonas koreensis TR6-01 & 1 & \\ Rhodobacteraceae & & \\ Rhodobacter Palaeoides 2.4.1 & 1 & 2.2 \\ Rhizobenzene & Rhizobium slettipitatecens B1 & 2 & 2.2 \\ Bacillus aquimaris TF-12 & 1 & \\ Bacillaceae & _Brevibacterium frigoritolerans_ DSM 8801 & 1 & 2.2 \\ \hline \hline \end{tabular} \({}^{1}\) RA: relative abundance.  
\end{table} 
Table 2: Putative classification and relative abundance of bacteria from groundwater. after electrophoresis. Eight of the fourteen isolated strains may possess atrazine-degrading genetic potential activity. PCR amplification of _trzN_ and _atzA_ genes showed positive results in a higher number of isolates than the rest of the degrading gene-coding enzymes, while _atzB_ and _atzE_ were amplified only in a single microorganism. Both genes -_trzN_ and _atzA_- and competent strains, initiated the degrading pathway by a hydrolytic dechlorinating reaction leading to a non-chlorinated more biodegradable s-triazine. _TrzN_ was the most detected gene, since five strains -GW38-4, GW38-6, GW38-7, GW38-10, and GW38-14-associated with _Microbacterium_, _Arthrobacterium_, _Nesterenkonia_, _Nocardioides_, and _Pseudomonas_, showed its