A strategy for optimizing quality and quantity of DNA extracted from soil

The efficiency of a bead beating method was studied in detail with regard t o a variety of factors including beating time and speed, volume and tempera ture of the buffer, as well as amount and type of beads employed. The resul ts presented here reveal that all of these parameters have a significant ef fect on yield and quality of DNA extracted from soils. Precise adjustment o f extraction conditions allows for significantly higher yields of high qual ity DNA from soils than previously reported, We further evaluated the effec t of the extraction conditions on the apparent soil microbial community str uctures, as observed by polymerase chain reaction (PCR) and RFLP. Differenc es in the fingerprints of DNA extracted under different conditions suggest that results could be biased when using gentle extraction procedures. Based on multiple subsequent extractions using very harsh extraction conditions, we propose a protocol for the quantification of the total DNA content in s oils. Extractions from six soils of different texture and chemical characte ristics with selected bead beating protocols revealed that the quality (fra gment size and purity) of the extracted DNA was generally very good, but al so depended on the soil characteristics. While a single, general protocol f or optimal DNA recovery from all soils cannot be given, this study provides detailed guidelines on how to optimize the general method to obtain optima l DNA from individual soils, (C) 2001 Elsevier Science B.V. All rights rese rved.