Pyrodictium delaneyi sp nov., a hyperthermophilic autotrophic archaeon that reduces Fe(III) oxide and nitrate

A hyperthermophilic, autotrophic iron and nitrate reducer, strain Su06(T), was isolated from an active deep-sea hydrothermal vent chimney on the Endeavour Segment in the north-eastern Pacific Ocean. It was obligately anaerobic, hydrogenotrophic and reduced Fe(III) oxide to magnetite and NO3- to N-2. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain was more than 97% similar to other species of the genera Pyrodictium and Hyperthermus. Therefore, overall genome relatedness index analyses were performed to establish whether strain Su06(T) represents a novel species. For each analysis, strain Su06(T) was most similar to Pyrodictium occultum PL-19(T). Relative to this strain, the average nucleotide identity score for strain Su06(T) was 72 %, the genome-to-genome direct comparison score was 13-19% and the species identification score at the protein level was 89 %. For each analysis, strain Su06(T) was below the species delineation cutoff. Based on its whole genome sequence and its unique phenotypic characteristics, strain Su06(T) is suggested to represent a novel species of the genus Pyrodictium, for which the name Pyrodictium delaneyi is proposed. The type strain is Su06(T) (= DSM 28599(T) = ATCC BAA-2559(T)).