Werner Arber

Our research interests center around molecular mechanisms of spontaneous alterations in the genetic information, i.e. genetic plasticity which is implied in the evolutionary process, together with natural selection and isolation. Bacteria and their viruses and plasmids are readily accessible to such investigations involving both molecular genetic and population genetic approaches. Long-term studies have been devoted to horizontal gene transfer mediated by viruses and plasmids, to restriction-modification systems and their implications on the efficiency of horizontal gene trander, as well as to molecular mechanisms of DNA recombination processes which lead to new DNA arrangements. Particular attention is given to transportation mechanisms of mobile genetic elements and to site-specific recombination systems. Various degrees of DNA target specificity render these DNA rearrangement mechanisms a natural source of genetic variation and thus of novel gene fusions and operon fusions. In varying growth conditions one can get insight into prevailing mechanisms of spontaneous mutagenesis in dependence of environmental conditions. Interestingly, many of these processes are mediated by enzymes acting as variation generators. Thus, the genes for the production of these enzymes are carried in the genome of each individual cell, although their action is exerted more or less by chance in relatively rare individuals of large populations. Genetic plasticity has its functional relevance at the population level insuring a steady process of microbial evolution. These notions are important for our world view and for risk evaluations of genetic engineering.