Comparison of different methods for the isolation and purification of total community DNA from soil

The efficiency and reproducibility of DNA extraction from soil was tested f or variations in lyric and purification treatments and their effect on yiel d and purity of DNA. The extraction yield was improved by increasing the co ncentration of EDTA or monovalent ions in isolation buffers,, by the introd uction of mechanical lysis treatments, and by the use of ethanol precipitat ion in place of PEG precipitation. Purity was improved using buffers with d ecreasing concentration of EDTA or by reducing the ionic strength of the bu ffer, and by all mechanical treatments. No lyric treatment was efficient on its own, the highest purity was achieved using Crombach buffer and a combi nation of bead-beating with lysozyme and SDS lysis followed by potassium ac etate and PEG precipitation, phenol/chloroform purification, isopropanol pr ecipitation, and spermine-HCl precipitation. Sonication sheared the DNA mor e than bead-heating. Lysozyme and SDS lysis without any mechanical treatmen ts allowed isolation of larger fragments (40-90 kb). Denaturing gradient ge l electrophoresis analysis of DNA isolated using a range of lyric treatment s revealed alterations in band patterns which might reflect differences in the efficiency of lytic treatments. (C) 1999 Elsevier Science B.V. All righ ts reserved.