Pseudonocardia abyssalis sp. nov. and Pseudonocardia oceani sp. nov., two novel actinomycetes isolated from the deep Southern Ocean.

The actinomycetes strains KRD168T and KRD185T were isolated from sediments collected from the deep Southern Ocean, and in this work, they are described as two novel species of the Pseudonocardia genus through a polyphasic approach. Despite sharing >99% 16S rRNA gene sequence similarity with other members of the genus, the comparative genomic analysis allowed the species delimitation based on Average Nucleotide Identity and digital DNA-DNA Hybridization. The KRD168T genome is characterised by a size of 6.31 Mbp and a G+C content of 73.44 %, while the KRD185T genome has a size of 6.82 Mbp and a G+C content of 73.98 %. Both strains contain meso-diaminopimelic acid as diagnostic diamino acid, glucose as the major whole-cell sugar, MK-8(H4) as a major menaquinone, and iso-branched hexadecanoic acid as a major fatty acid. Biochemical and fatty acid analyses also revealed differences between these strains and their phylogenetic neighbours, supporting their status as distinct species. The names Pseudonocardia abyssalis sp. nov. KRD168T (=DSM 111918T =NCIMB 15270T) and Pseudonocardia oceani KRD185T (=DSM 111919T =NCIMB 15269T) are proposed.