The Piezo-Hyperthermophilic Archaeon Thermococcus piezophilus Regulates Its Energy Efficiency System to Cope With Large Hydrostatic Pressure Variations.

Deep-sea ecosystems share a common physical parameter, namely high hydrostatic pressure (HHP). Some of the microorganisms isolated at great depths have a high physiological plasticity to face pressure variations. The adaptive strategies by which deep-sea microorganisms cope with HHP variations remain to be elucidated, especially considering the extent of their biotopes on Earth. Herein, we investigated the gene expression patterns of Thermococcus piezophilus, a piezohyperthermophilic archaeon isolated from the deepest hydrothermal vent known to date, under sub-optimal, optimal and supra-optimal pressures (0.1, 50, and 90 MPa, respectively). At stressful pressures [sub-optimal (0.1 MPa) and supra-optimal (90 MPa) conditions], no classical stress response was observed. Instead, we observed an unexpected transcriptional modulation of more than a hundred gene clusters, under the putative control of the master transcriptional regulator SurR, some of which are described as being involved in energy metabolism. This suggests a fine-tuning effect of HHP on the SurR regulon. Pressure could act on gene regulation, in addition to modulating their expression.

Thermococcus piezophilus sp. nov., a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth, isolated from a deepest hydrothermal vent at the Mid-Cayman Rise.

A novel strictly anaerobic, hyperthermophilic archaeon, designated strain CDGST, was isolated from a deep-sea hydrothermal vent in the Cayman Trough at 4964m water depth. The novel isolate is obligate anaerobe and grows chemoorganoheterotrophically with stimulation of growth by sulphur containing compounds. Its growth is optimal at 75°C, pH 6.0 and under a pressure of 50MPa. It possesses the broadest hydrostatic pressure range for growth that has ever been described for a microorganism. Its genomic DNA G+C content is 51.11mol%. The novel isolate belongs to the genus Thermococcus. Phylogenetic analyses indicated that it is most closely related to Thermococcus barossii DSM17882T based on its 16S rRNA gene sequence, and to 'Thermococcus onnurineus' NA1 based on its whole genome sequence. The average nucleotide identity scores with these strains are 77.66% for T. barossii and 84.84% for 'T. onnurineus', respectively. Based on the draft whole genome sequence and phenotypic characteristics, strain CDGST is suggested to be separated into a novel species within the genus Thermococcus, with proposed name Thermococcus piezophilus (type strain CDGST=ATCC TSD-33T=UBOCC 3296T).

Complete Genome Sequence of the Hyperthermophilic and Piezophilic Archeon Thermococcus piezophilus CDGST, Able To Grow under Extreme Hydrostatic Pressures.

We report the genome sequence of Thermococcus superprofundus strain CDGS(T), a new piezophilic and hyperthermophilic member of the order Thermococcales isolated from the world's deepest hydrothermal vents, at the Mid-Cayman Rise. The genome is consistent with a heterotrophic, anaerobic, and piezophilic lifestyle.