Cesium chloride-bisbenzimide gradients for separation of phytoplasma and plant DNA.

CsCl-bisbezimide gradient centrifugation is a method to separate phytoplasma from host plant DNA. Bisbenzimide forms a complex with A + T-rich DNA thereby lowering its relative density. During centrifugation the A + T-rich phytoplasma DNA is spatially separated from the less A + T-rich host plant DNA. The difference in buoyant density between phytoplasma DNA and plant DNA varies according to the host-pathogen combination. The phytoplasma DNA forms a distinct band above the host plant DNA and can be collected. Depending on the phytoplasma titer and the scale of extraction, highly purified DNA is obtained in sufficient quantities for the construction of a genomic library, a sequencing project or hybridization studies.