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Bacterial plasmids are important agents of genetic exchange and their study is vital both for emerging genetic engineering techniques and for better understanding of how microbial populations evolved. Plasmid transfer occurs in many different forms and environments, and there is a large number of laboratories working on different aspects of the problem. This Network aims to encourage greater communication and exchange of ideas between these laboratories, and in particular to bring the two main groups of scientists working in the field - microbial ecologists, and molecular biologists - closer together.
Genetic exchange between different organisms in general has been recognised as a major force in evolution, particularly of microbial populations. It is also highly relevant for the debate about releasing genetically manipulated organisms (GMOs) into the environment, given the potential for transferring the new genes into other organisms.
Bacterial plasmids (small circles of DNA independent of the main bacterial chromosome that can be transmitted independently between bacteria, even of different species) spread genes readily within the natural environment by conjugative transfer between bacteria. Transposable elements play a vital role in this process, aiding the recruitment of new genes to self transmissible plasmids and promoting the formation of novel combinations of complementary functions.
Of the two major groups studying plasmid biology, molecular biologists have been dissecting the mechanisms of plasmid replication, stable inheritance and conjugative transfer in tightly controlled laboratory environments. Microbial ecologists on the other hand have been studying plasmid survival and spread in either natural or model microcosms outside the laboratory. Both lines of study can be enriched by greater exchange of information between them, which the Network has set out to encourage, partly through a series of highly goal-oriented workshops where current aims, experimental approaches and ideas will be exchanged.
Microbial ecologists have been pursuing two main lines in this area. The first involves introducing well studied plasmids into natural or model microcosms to study their survival and spread, and factors that influence these. A great deal is already known about the genetic and functional organisation of these plasmids, and there is great potential to design experiments that identify which factors are most important in determining how well plasmids persist and spread in the environment. So far this has not been done because of the lack of regular contacts between those doing the ecological experiments, and those with detailed knowledge of the plasmids. This Network will attempt to rectify this by bringing these groups together.
The second area of study for microbial ecologists is behaviour of plasmids in new environments created by human activity, such as hospitals, or soil contaminated by industrial waste. Efficient techniques for identifying and classifying the methods of replication, maintenance and transfer of plasmids that determine their potential to survive and spread are needed, and again this study aims to bring together those that require the expertise for experiments and those that possess it.
On the molecular biology front, a better understanding of different features of plasmid replication, maintenance and transfer and their relative relevance requires ecological experiments in "natural" conditions. This has already been demonstrated by current research, for example in factors that limit plasmid reproduction. For example the plasmid pPS10 was found to replicate in Escherichia coli at 25°C but not at 37°C.
It can therefore be seen that both avenues of research can gain from the other. Europe has probably the largest number of first-rate groups working in both areas, and the ESF Network should raise our understanding of the role of plasmids as agents of gene spread to an unmatched level.
This Network was approved by the ESF Executive Council in June 1994 for a three-year period.
