Persistence of DNA in the Environment and Its Potential for Bacterial Genetic Transformation

Abstract

Previously it was assumed that naked DNA molecules appearing in bacterial habitats such as in soil, sediment or freshwater and sea water would almost instantaneously be degraded by nucleolytic enzymes. Such enzymes are known to be released from microorganisms including bacteria, yeasts and fungi which live in the terrestrial and aquatic environment. The low molecular weight degradation products of biological macromolecules provided by the action of extracellular enzymes can serve as nutrients for the microorganisms. More recently, experimental data suggest that extracellular DNA in terrestrial environments can persist for considerable time periods. The persistence appears to depend on additional parameters besides the presence and activity of extracellular DNases. Some of these findings will be summarized in the following. Further, the phenomenon of natural genetic transformation in bacteria has been documented for an increasing number and a wide variety of bacterial species (for references, see Lorenz and Wackernagel 1994). Natural transformation is the ability of bacteria to take up DNA actively, to inherit such DNA and to express its genetic information (Lorenz and Wackernagel 1994).