Most bacterial lineages are known only by molecular sequence data from environmental surveys and represent the uncultivated majority. One of these lineages, candidate phylum FBP, is widespread in extreme environments on Earth, ranging from polar and desert ecosystems to wastewater and contaminated mine sites. Here we report on the characterization of strain LMG 29911(T), the first cultivated representative of the FBP lineage. The strain was isolated from a terrestrial surface sample from Utsteinen, Sor Rondane Mountains, East Antarctica and is a Gram-negative, aerobic, oligotrophic chemoheterotrophic bacterium. It displays growth in a very narrow pH range, use of only a limited number of carbon sources, but also a metabolism optimized for survival in low-nutrient habitats. Remarkably, phenotypic and genome analysis indicated an extreme resistance against antibiotics and toxic compounds. We propose the names Abditibacterium utsteinense for this bacterium and Abditibacteriota for the former candidate phylum FBP. Furthermore, inter- and intra-phylum relationships indicate Armatimonadetes, a neighboring lineage to the Abditibacteriota, to be a superphylum.