ABSTRACT
Two approaches have been developed with variations for the recovery of DNA from soils and sediments. The cell extraction approach involves the separation of bacterial cells from soil or sediment particles by differential centrifugation followed by lysis of the recovered cells, and recovery of the DNA. The direct lysis method involves release of DNA from the cells by physical disruption, without separating the cells from the soil or sediment matrix, followed by extraction and purification of the DNA. One variation of this method uses a bead beater to disrupt cells, alkaline extraction of the DNA in buffer, and purification of the extracted DNA by ethanol precipitation, cesium chloride density gradient centrifugation, and hydroxyapatite column chromatography. Another variation uses freeze-thaw cycling to disrupt the cells followed by phenol-chloroform extraction, and column chromatographic purification of the DNA.
