Table 3.

Decrease in amplification efficiency caused by coamplified competitor DNA in a real-time competitive PCRa

Competitor DNA copy no.bAvgKm c ± SDAvg ɛd ± SD
 00.1012 ± 0.00180.7166 ± 0.0036
100 0.0926 ± 0.00310.6983 ± 0.0071
101 0.0849 ± 0.00550.6793 ± 0.0140
102 0.0901 ± 0.00330.6925 ± 0.0076
103 0.0543 ± 0.00210.5757 ± 0.0095
104 0.0183 ± 0.00030.3143 ± 0.0036
105 0.0094 ± 0.00040.1896 ± 0.0068
106 0.0084 ± 0.00000.1736 ± 0.0004
107 0.0124 ± 0.00110.2364 ± 0.0162
108 0.0120 ± 0.00120.2300 ± 0.0181
  • a See Fig. 8.

  • b All reaction mixtures contained 103 genomic copies of Synechococcus sp. strain BO 8807, which is detected by specific TaqMan probe S8807A, and variable amounts of competitor DNA (Synechococcus sp. strain BO 8809), as indicated. The competitor was not detected by the TaqMan probe (see Fig. 8 for details).

  • c Km was derived from a nonlinear least-squares fit of the PCR between cycles 1 and 35 using the equation ΔRQ (i+1) = ΔRQ i[1 +Km RQi + Km )−1].

  • d Amplification efficiency at a fluorescence threshold (ΔRQ) of 0.04 was calculated as follows: ɛ =Km (0.04 +Km −1).