2.7. Microbial community as determined by denaturing gradient gel electrophoresis
The samples for microbial community analysis were collected before and after 5 days of the experiment. Root and soil samples were initially homogenized using a tissue grinder and sonicator. Water samples were filtrated through a 0.2 μm filter membrane (Nuclepore, Whatman, UK).
Total genomic DNA was extracted from the samples using the SDS-based method as described previously by Zhou et al. (Zhou et al., 1996) and purified by using the Gel/PCR DNA fragments extraction kit (Geneaid, Taiwan). The purified DNA was used as a template for amplification of the partial 16S rDNA fragment of the domain Bacteria using Taq DNA polymerase (Invitrogen, USA) according to the manufacturer's protocol with