FIGURE 1.

Schematic diagram of the optimization process. In Stage 1 of the process, various extraction kits and Nicolaisen’s method (as listed in Table 1) was tested on soils FH and FL (see text for soil descriptions). In Stage 2, various extraction buffers, lysis conditions, and nucleic acid precipitants were tested using Nicolaisen’s method as the base, creating a new “semi-optimized Nicolaisen’s method.” In the final Stage 3, DNases/reverse transcriptases and purification kits were tested concurrently for their ability to completely remove genomic DNA, and was briefly tested in combination. The end result is the “Modified Nicolaisen’s method,” which is based on the workflow as outlined in Figure 2.