Figure 1.
Preparation and quality control of E. coli DNA reference standard.
(A) Analysis of E. coli genomic DNA with full wavelength scanning (240–350 nm). (B) Results of Agarose Gel electrophoresis for E. coli genomic DNA. M, λ-Hind III digest DNA marker. Lane 1, E. coli genomic DNA.
Figure 2.
Trend of OD260/OD280 in collaborative calibration study for E. coli DNA reference standard.
Table 1.
The calibration results of E. coli DNA content by UV absorption (μg/mL).
Figure 3.
Stability of E. coli DNA reference standard.
(A) The content and OD260/OD280 of E. coli DNA reference stored under four different temperatures for four months. (B) The electrophoresis of E. coli DNA reference stored under four different temperatures for four months. Because of high DNA content, some genomic DNA was stuck in the well. (C) The electrophoresis of E. coli DNA reference stored at −20°C for 24 months.
Figure 4.
Results of real-time PCR for E. coli DNA reference standard.
(A) Standard curve. Ct was plotted against each concentration (Log Co). Ct represents the cycle at which reporter signal was first detected. (B) Amplification curves. 1–6: 102, 10, 1, 1×10−1, 1×10−2, 1×10−3 pg/μL. (C) Melting curves. It showed primer pair was specific for E. coli DNA.
Table 2.
Results of PicoGreen assay for E. coli DNA reference.
Figure 5.
The consistency analysis of E. coli DNA reference standard using PicoGreen fluorescence method.