QC-PCR carried out on log cells of P. fluorescens CHA0 (A, 4 × 106 cells/ml; B, 2 × 106 cells/ml; C, 1 × 106 cells/ml; D, 5 × 105 cells/ml; E, 2.5 × 105 cells/ml) against twofold dilutions of competitor oligonucleotide. Lanes: 1, 2.5 × 10−4 μg/ml; 2, 1.25 × 10−4 μg/ml; 3, 6.25 × 10−5 μg/ml; 4, 3.13 × 10−5 μg/ml; 5, 1.57 × 10−5 μg/ml; 6, 7.81 × 10−6 μg/ml; 7, 3.92 × 10−6 μg/ml; 8, 1.96 × 10−6 μg/ml; M, 100-bp ladder; cd, cell DNA alone (left, 4 × 106 cells/ml; right, 2.5 × 105 cells/ml); co, competitor oligonucleotide alone (left, 2.5 × 10−4 μg/ml; right, 3.13 × 10−5 μg/ml); N, negative control (blank). Reactions yielding two bands of the same intensity are indicated by an asterisk.