Abstract
High-molecular-weight DNA (HMW DNA) extracted from soil is useful for examined the functions and diversity of soil organisms, the majority of which are difficult to culture. In the present study, the procedures used to extract HMW DNA from soil samples were improved. The grinding of soil samples with liquid nitrogen followed by a lysozyme treatment at 45°C for 1 h and an incubation with protease and SDS at 50°C for 5 h increased the size and yield of HMW DNA extracted from these samples. In the soil group Andosols, the addition of boiled sonicated salmon DNA was effective for HMW DNA extraction.