Moritella profunda sp. nov. and Moritella abyssi sp. nov., two psychropiezophilic organisms isolated from deep Atlantic sediments

Two novel psychropiezophilic bacteria, Moritella profunda and Moritella abyssi, were isolated from deep Atlantic sediments at 2815 m depth off the West African coast. Both organisms are strictly psychrophilic with optimal growth temperatures of 2°C and 4–5°C respectively, and maximum temperatures of 12°C and 14°C. They are moderately piezophilic, showing intermediate pressure adaptations between non-piezophilic Moritella marina and obligate piezophile Moritella yayanosii. M. profunda exhibits optimal pressure at 20–24 MPa at 6°C, while M. abyssi shows optimal growth at 19–20 MPa at the same temperature. Both strains are Gram-negative, motile rods; facultatively anaerobic; and oxidase-positive. Polyphasic taxonomic analysis including 16S rRNA sequencing, DNA–DNA hybridization, and fatty acid composition confirmed their classification as distinct Moritella species. The strains share characteristic features of the genus including Q-8 quinone and docosahexaenoic acid. Both exhibit an interesting temperature-pressure relationship where elevated temperature increases piezophily, likely reflecting molecular compromises in enzyme adaptation between requirements for flexibility at low temperature and rigidity under high pressure.

Key findings

• Two novel Moritella species (M. profunda and M. abyssi) isolated from 2815 m Atlantic sediments show strictly psychrophilic growth with maximal rates at 2°C and 4–5°C respectively
• Both organisms are moderately piezophilic with optimal pressures (20–24 MPa and 19–20 MPa) lower than ambient pressure at isolation site, representing an intermediate phenotype between non-piezophilic and obligate piezophile Moritella species
• Elevated temperature increases piezophily in both strains, demonstrating temperature-pressure coupling likely reflecting adaptive compromises in enzyme structure and function
• 16S rRNA analysis and DNA–DNA hybridization confirmed distinct species status with <60% DNA similarity to existing Moritella species