This book gives an overview of gene transfer and stability in those aquatic and terrestrial environments where bacteria and fungi can survive and interact genetically. It examines the role played by sex between microbes in the evolution of populations and their survival. Special emphasis is placed on methodology, including the analysis by novel techniques of genetic material extracted directly from soils, rivers and lakes. The natural spread of antibiotic resistance and the safe use of genetically manipulated microbes are matters of considerable scientific, medical and public concern upon which the investigations presented here have direct bearing. This unique collection will be of value to specialist researchers in applied microbiology, ecology and biotechnology as well as biomedical scientists interested in the environmental risks of genetic engineering.