<jats:title>ABSTRACT</jats:title> <jats:p> The pseudocolonial coral <jats:italic>Lophelia pertusa</jats:italic> (Scleractinia, Caryophylliidae) is a eurybathic, stenothermal cosmopolitan cold-water species. It occurs in two color varieties, white and red. <jats:italic>L. pertusa</jats:italic> builds vast cold-water coral reefs along the continental margins, which are among the most diverse deep-sea habitats. Microbiology of <jats:italic>L. pertusa</jats:italic> has been in scientific focus for only a few years, but the question of whether the coral holds a host-specific bacterial community has not been finally answered. Bacteria on coral samples from the Trondheimsfjord (Norway) were characterized by the culture-independent 16S rRNA gene-based techniques terminal restriction fragment length polymorphism and sequence analysis. <jats:italic>L. pertusa</jats:italic> revealed a high microbial richness. Clone sequences were dominated by members of the <jats:italic>Alpha</jats:italic> - and <jats:italic>Gammaproteobacteria</jats:italic> . Other abundant taxa were <jats:italic>Bacteroidetes</jats:italic> , <jats:italic>Actinobacteria</jats:italic> , <jats:italic>Verrucomicrobia</jats:italic> , <jats:italic>Firmicutes</jats:italic> , and <jats:italic>Planctomycetes</jats:italic> . The bacterial community of <jats:italic>L. pertusa</jats:italic> not only differed conspicuously from that of the environment but also varied with both the location and color variety of its host. Therefore, the microbial colonization cannot be termed “specific” sensu stricto. However, similarities to other coral-bacterium associations suggest the existence of “cold-water coral-specific” bacterial groups sensu lato. <jats:italic>L. pertusa</jats:italic> -associated bacteria appear to play a significant role in the nutrition of their host by degradation of sulfur compounds, cellulose, chitin, and end products of the coral's anaerobic metabolism. Some coral-associated microbes were regarded as opportunistic pathogens. Dominance of mixotrophic members of the <jats:italic>Rhodobacteraceae</jats:italic> in white <jats:italic>L. pertusa</jats:italic> could explain the wider dispersal of this phenotype by supplementary nutrition. </jats:p>