FIG. 1.

Protocols showing successive treatments for direct in situ lysis of soil microorganisms for DNA extraction. For details, see Materials and Methods. Protocol 1 consists of extraction of extracellular DNA from dried soil, with no lysis treatment. Protocol 2 includes grinding of dried soil followed by DNA extraction. Protocol 3 includes soil grinding followed by homogenization in the extraction buffer using an Ultraturrax mixer. In protocols 4a and b, soil grinding and homogenization are followed by sonication using a titanium microtip sonicator (protocol 4a) or a Cup Horn sonicator (protocol 4b). Protocols 5a and b include soil grinding, homogenization, and sonication using a microtip (protocol 5a) or a Cup Horn (protocol 5b) sonicator, followed by chemical and enzymatic lysis.