TABLE 3.

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

Competitor DNA copy no.b	Avg Kmc ± SD	Avg ɛd ± SD
0	0.1012 ± 0.0018	0.7166 ± 0.0036
100	0.0926 ± 0.0031	0.6983 ± 0.0071
101	0.0849 ± 0.0055	0.6793 ± 0.0140
102	0.0901 ± 0.0033	0.6925 ± 0.0076
103	0.0543 ± 0.0021	0.5757 ± 0.0095
104	0.0183 ± 0.0003	0.3143 ± 0.0036
105	0.0094 ± 0.0004	0.1896 ± 0.0068
106	0.0084 ± 0.0000	0.1736 ± 0.0004
107	0.0124 ± 0.0011	0.2364 ± 0.0162
108	0.0120 ± 0.0012	0.2300 ± 0.0181

^aSee Fig. 8. 

^bAll 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). 

^cK_m 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 + K_m(ΔRQ_i + K_m)⁻¹]. 

^dAmplification efficiency at a fluorescence threshold (ΔRQ) of 0.04 was calculated as follows: ɛ = K_m(0.04 + K_m⁻¹).