Although bacteria are important in many biotechnological industries including food, pharmaceuticals and agriculture, and are among the best-known organisms in terms of their genomes and laboratory genetics, paradoxically their population genetics and interactions outside the laboratory, especially in soil, are poorly understood. The biotechnological significance of this is clear: it is relatively easy to make novel genetic constructs, but difficult to predict the consequences of releasing them in the field. Bacterial population genetics urgently requires further development, both more empirical knowledge (from new molecular tools and better strategies for sampling populations) and a firmer theoretical framework (especially a clearer understanding of the relative importance of different gene transfer processes.
This project will provide baseline knowledge of the genetic structure of indigenous populations of rhizobia in field soils, and assess the impact of GM releases of rhizobia (and, by analogy, other bacteria used as agricultural soil inoculants) against this baseline. Gene flow within rhizobial populations, between rhizobia and other bacterial groups, and between GM release strains and the indigenous community will be analysed, and the maintenance of genes and the fluctuations in the genetic composition of populations that arise through normal agricultural practice will be examined. Rhizobia, the nitrogen-fixing symbionts of legumes, are priority organisms for such studies and an excellent model because they are of biotechnological importance and essential for developing sustainable agricultural systems. They survive in soil and colonise the rhizosphere in addition to their important role in biological nitrogen fixation. The use of commercial rhizobial inoculants is an established agricultural practice, with a long history of agronomic, genetic and ecological studies and there is potential for commercial use of modified strains in the future.