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

Abstract

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).

Fig. 1.

Transmission electron micrograph of strain Su06^T using 1–2% uranyl acetate as a negative stain showing lophotrichous flagellation of a coccoid-shaped cell. Bar, 500 nm.

Fig. 2.

Neighbour-joining tree showing the position of strain Su06^T within the order Desulfurococcales based on sequences of the 16S rRNA gene (1305 nt). GenBank/EMBL/DDBJ accession numbers are included in parentheses. The topology of the tree was estimated by bootstrap analysis based on 500 replications. Numbers at branch points are the percentage support by bootstrap analysis. Bar, 1% sequence divergence.