Extraction and purification of microorganisms total DNA from red soil

Direct extraction of soil DNA has become essential for the study of soil microorganisms.Here,we used two different direct methods of extracting DNA from four types red soil and purified the soil DNA using Sephadex G-200 gel filtration.The result shows that both of the two procedures can obtain DNA fragment over 10 kb from soil.But the yields of DNA with different methods are different.Method two was found to be the best DNA extraction procedure in which freeze thawing combined with SDS and lysozyme.It is of high production and good reproducibility and is suitable for extracting DNA from small amount of soil sample.Sephadex G-200 spin column purification was found to be the best method for removing humic substances while minimizing DNA loss during purification.