Research Interests:  Symbiotic bacteria are a key yet poorly understood facet of our natural world. Yet humans and our food sources often depend on the cooperation of bacterial symbionts for health and fitness. Current research is beginning to unravel the molecular and selective basis of bacterial cooperation. In the process we are discovering that beneficial infections are often evolutionarily unstable and more dynamic than expected. In the Sachs Lab we investigate the forces that shape bacterial cooperation with hosts as well as the origins and evolution of harmful strains. Our current empirical focus is on rhizobial bacteria that live in soils throughout the world and nodulate the roots of many legume hosts. Projects in the Sachs Lab often utilize a wide range of techniques to answer basic questions. These include field collections of wild bacteria, experimental infections and experimental evolution, sequencing and phylogenetic analysis.