Table 5. Assessment of yield and purity of the DNA extracted by method M2 and its modification (glass beads, glass powder and glass powder + powdered activated charcoal).
| Method/Soil | Glass Beads | Glass Powder | Glass Powder + PAC | ||||||
|---|---|---|---|---|---|---|---|---|---|
| DNA yield (μg/g) | A260/280 | A340 | DNA yield (μg/g) | A260/280 | A340 | DNA yield (μg/g) | A260/280 | A340 | |
| Garden soil | 3.3 ± 0.05 *** | 1.50 ± 0.03 | 0.06 ± 0.04 | 5.5 ± 0.07 *** | 1.50 ± 0.01 | 0.03 ± 0.02 | 6.2 ± 0.04 | 1.80 ± 0.03 | 0.05 ± 0.02 |
| Sewage sludge | 1.2 ± 0.03 **** | 1.45 ± 0.04 | 0.06 ± 0.03 | 5.8 ± 0.07 ns | 1.52 ± 0.03 | 0.06 ± 0.05 | 5.9 ± 0.03 | 1.69 ± 0.04 | 0.03 ± 0.02 |
| Lake soil | 1.0 ± 0.07*** | 1.30 ± 0.02 | 0.13 ± 0.07 | 4.2 ± 0.15 ns | 1.42 ± 0.04 | 0.07 ± 0.04 | 4.4 ± 0.03 | 1.73 ± 0.04 | 0.03 ± 0.02 |
| Compost | 3.0 ± 0.18 *** | 1.44 ± 0.05 | 0.09 ± 0.06 | 4.1 ± 0.15 ** | 1.50 ± 0.04 | 0.08 ± 0.04 | 5.0 ± 0.09 | 1.74 ± 0.06 | 0.04 ± 0.05 |
DNA concentration (μg/mL) was quantified in a spectrophotometer (A260 nm).
Yield in μg per gram of soil = concentration of DNA (μg/μL). Volume used to suspend DNA (μL) /weight of soil (g).
A260/280 represents protein contamination. A340 is an indication for humic acid presence.
PAC represents powdered activated charcoal.
P values were generated by Graph Pad Prism 5.0 software using paired T-test analysis.
P value < 0.05 is considered to be statistically significant. DNA extraction methods performing worse at a statistically significant level as compared with the best performing method (Glass powder + PAC) are indicated by asterisks
**** indicates P < 0.0001
*** indicates P < 0.001
** indicates P < 0.01
ns indicates P > 0.05 which is statistically non-significant.