This study seeks to determine the prevalence, allele diversity, mobility and epidemiology of blaTEM (ampicillin) resistance genes and their hosts in a broad range of clinical and environmental settings. Recent studies suggest that environmental population s of bacteria can be an important reservoir of resistance genes of clinical importance. The usual organism-oriented investigation of bacterial populations cannot easily be applied to understand the ecolo gy of antibiotic resistance since most of the resis tance traits are linked to mobile genetic elements that transcend species barriers and the reproduction behavior of single-celled organisms. The increasing challenge from clinical resistance development does therefore advocate a broader examination of res istance gene reservoirs and also a shift in focus from organism-oriented studies to the investigation of the ecology of the genetic trait itself as an independent functional unit. This project takes on a broad ecosystem perspective that would significantl y enhance our capability to understand the evolutionary origins, reservoirs, dynamics and host interactions encountered by antibiotic resistance genes in their natural ecosystem. The ecology of blaTEM genes conferring ampicillin resistance will be determi ned from analysis of a broad range of clinical and environmental samples from Norway and adjacent marine and Arctic areas.