Table 3.

Presence of PCR inhibitory effects after using different soil DNA extraction protocols

Sample	ΔCTa
	SoilMaster kit		FastDNA kit		Protocol of this study
	Without BSA	With BSA	Without BSA	With BSA	Without BSA	With BSA
S 01	Inhibited	0.88 ± 0.55	Inhibited	1.65 ± 0.08	Inhibited	1.47 ± 0.23
S 03	Inhibited	0.32 ± 0.06	Inhibited	0.74 ± 0.20	Inhibited	1.21 ± 0.19
S 04	Inhibited	0.93 ± 0.12	Inhibited	1.74 ± 0.27	Inhibited	1.49 ± 0.15
S 05	0.86 ± 0.31	0.32 ± 0.13	>6.55b	0.01 ± 0.18	Inhibited	0.74 ± 0.26
S 06	13.47± 1.38	0.33 ± 0.06	Inhibited	0.08 ± 0.04	Inhibited	1.13 ± 0.12
S 07	1.59 ± 0.14	0.27 ± 0.06	Inhibited	0.04 ± 0.05	Inhibited	0.68 ± 0.32
S 10	1.31 ± 0.23	0.07 ± 0.10	Inhibited	0.06 ± 0.10	Inhibited	−0.19 ± 0.26
S 12	2.45 ± 0.45	0.59 ± 0.08	Inhibited	−0.06 ± 0.21	Inhibited	0.47 ± 0.20
S 92	Inhibited	0.79 ± 0.15	Inhibited	0.57 ± 0.26	Inhibited	1.22 ± 0.15
S 95	0.64 ± 0.11	0.36 ± 0.03	>4.83b	−0.11 ± 0.30	Inhibited	0.30 ± 0.11
Overall ΔCT		0.48 ± 0.09		0.47 ± 0.22		0.85 ± 0.17

^aThe degree of PCR inhibition is reflected by the cycle threshold difference (ΔC_T), which was calculated by subtracting C_T values of the PCR of soil DNA extracts with the incorporation of a noncompetitive internal amplification control (IAC) from C_T values of the PCR mixture containing the IAC as a single template (control). PCRs with ΔC_T values greater than 2 were considered to be strongly inhibited (boldface). Data are the means and standard errors of the means (SEM) of results from three independent experiments. “Inhibited” indicates that no PCR amplification signal could be detected in three subsamples after 60 cycles.

^bPCR amplification signal could be detected in only one or two subsamples after 60 cycles.