Supplemental Information Evaluation of PCR-based Quantification Techniques to Estimate the Abundance of Atrazine Chlorohydrolase Gene atzA in Rhizosphere Soils

Primers were selected from Shapir et al. 2008 with the one base pair correction listed in the Material and Methods section. Primer specificity was tested by nucleotide BLAST search analysis (NCBI, http://blast.ncbi.nlm.nih.gov/Blast.cgi) for possible binding partners in Pseudomonas sp. strain ADP chromosomal and plasmid DNA, as well as for binding sites on identified sequences obtained from exogenous soil bacteria. We found no identified amplicons detected outside of the atzA gene in Pseudomonas. Results among exogenous soil bacteria include species which contain atzA homologs, such as Herbasprillium sp. and Arthobacter sp. As such, these primers would selectively amplify only atzA (and homologs such as smzA) and we proceeded to use the primers listed in Table 1.