The PCR products were purified using the MEGA quick-spinTM (Intron Biotechnology, Inc) and the purity and concentration of
DNA in each sample were measured using a Nanodrop ND-1000 spectrophotometer and number of copies of
a template DNA per ml of elution buffer was calculated accordingly. Standard-curves were prepared using
serial dilution of PCR products from pure cultures for the different bacterial groups (Chen et al., 2015).