Draft Genome Sequence of Pyrodictium occultum PL19T, a Marine Hyperthermophilic Species of Archaea That Grows Optimally at 105°C

Pyrofollis japonicus gen. nov. sp. nov., a novel member of the family Pyrodictiaceae isolated from the Iheya North hydrothermal field

A novel hyperthermophilic, heterotrophic archaeon, strain YC29T, was isolated from a deep-sea hydrothermal vent in the Mid-Okinawa Trough, Japan. Cells of strain YC29T were non-motile, irregular cocci with diameters of 1.2-3.0 µm. The strain was an obligatory fermentative anaerobe capable of growth on complex proteinaceous substrates. Growth was observed between 85 and 100 °C (optimum 90-95 °C), pH 4.9-6.4 (optimum 5.1), and in the presence of 1.4-4.0% (w/v) NaCl (optimum 3.0%). Inorganic carbon was required as a carbon source. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolate was a member of the family Pyrodictiaceae. The genome size was 2.02 Mbp with a G+C content of 49.4%. The maximum values for average nucleotide identity (ANI), average amino acid identity (AAI), and in silico DNA-DNA hybridization (dDDH) value of strain YC29T with relatives were 67.9% (with Pyrodictium abyssi strain AV2T), 61.1% (with Pyrodictium occultum strain PL-19T), and 33.8% (with Pyrolobus fumarii strain 1AT), respectively. Based on the phylogenetic, genomic, and phenotypic characteristics, we propose that strain YC29T represents a novel genus and species, Pyrofollis japonicus gen. nov., sp. (type strain YC29T = DSM 113394T = JCM 39171T).

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

A hyperthermophilic, autotrophic iron and nitrate reducer, strain Su06T, 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 N2. 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 Su06T represents a novel species. For each analysis, strain Su06T was most similar to Pyrodictium occultum PL-19T. Relative to this strain, the average nucleotide identity score for strain Su06T 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 Su06T was below the species delineation cutoff. Based on its whole genome sequence and its unique phenotypic characteristics, strain Su06T is suggested to represent a novel species of the genus Pyrodictium, for which the name Pyrodictium delaneyi is proposed. The type strain is Su06T (=DSM 28599T=ATCC BAA-2559T).