The taxonomic positions of two actinobacterial strains isolated from Mariana Trench sediment were established using a combination of genotypic and phenotypic data. The strains, isolates MT2.1(T) and MT2.2(T), formed a distinct phyletic line in the Micrococcineae 16S rRNA gene tree together with Dermacoccus abyssi NCIMB 14084(T). The isolates had chemical and phenotypic properties typical of members of the genus Dermacoccus and could be distinguished sharply from one another and from the type strains of Dermacoccus abyssi and Dermacoccus nishinomiyaensis using DNA-DNA relatedness data. A range of phenotypic properties served to distinguish the two novel strains from one another and from the type strains of established Dermacoccus species. The G+C contents of the DNAs of strains MT2.1(T) and MT2.2(T) were 66.8 and 69.1 mol%, respectively. It is evident that the two isolates merit recognition as novel species within the genus Dermacoccus. The names proposed for these taxa are Dermacoccus barathri sp. nov. (type strain MT2.1(T)=DSM 17574(T)=NCIMB 14081(T)) and Dermacoccus profundi sp. nov. (type strain MT2.2(T)=DSM 17575(T)=NCIMB 14126(T)) [corrected]