African Journal of Biotechnology

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Persistence of plasmid DNA in different soils

M Kandhavelu, SJ Vennison


Natural genetic transformation is believed to be the essential mechanism for the attainment of genetic plasticity in many species of bacteria. Dying cells are likely to release naked DNA that may survive for many hours. Although numerous studies have shown that horizontal gene transfer between distantly related genera, but how long that DNA persists in the environment is yet be reported. We present evidence from studying the plasmid DNA retaining capability of different sterilized/abiotic soils (red, black, river, silt and loose sand soils). The study also explains how long DNA molecules are in the active transformable form in the above soils. Plasmid DNA after purification was quantified and 2 ƒÊg DNA was mixed in 2 kg of sterile soils having less than 20% moisture and experimental set up was maintained in laboratory conditions at 31oC. Every 7 days 1 g of soil was taken, DNA purified from it and then that DNA was used for transformation with the E. coli DH5∝ competent cells and the results showed that DNA would persist till 35 days and it had transforming ability.

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